Of all the video games I've played, The Elder Scrolls IV: Oblivion is probably still my favourite of all time. Since the greatest joy of a Bethesda game typically lies in the exploration of the world, the ability to purchase and upgrade a home is important as it provides a feeling of putting down roots. Homes also let you stash items that you don't wish to carry or sell and strategic placement of these objects can give a sense of identity to your character.
Unfortunately, homes and upgrades cost a huge amount of money compared to most other things in the game. Or maybe you'll actually try to follow popular advice and Train 5 times per level, which is very expensive in the early game. Upon figuring out how little money simply playing through quests pays directly, you'll likely find yourself looking for ways to deliberately earn coin.
What follows is a list the main occupational earning possibilities available to a player character – at least in the original version of the game. I expect this advise will hold true for the Remaster but it will be a little time before I can confirm this. (On the other hand, the Remaster's release is why I figured it was worthwhile to write such a guide for a very old game).
Scavenger
The simplest way to get a little coin in Oblivion is to take items you are legally allowed to take and sell them. The Imperial City in particular is full of crates containing small amounts of goods and even a few coins. A remarkable number of cultivated crops in farms are also free to take – even the vineyards just outside of Skingrad are full of grapes you can hoover up with impunity. This is probably the least effective way to get rich but it is the foundational way to get money.
Thief
If your aim is to grab items and sell them, not discriminating between owned and unowned goods is likely to net you a better haul. Pickpocketing is always a roll of the dice but stealing from houses and castles is basically risk free if you only grab when the stealth eye symbol shows that you are hidden. Murdering people for their stuff like a bandit isn't a profitable option because the law enforcers of the Empire are as all-seeing as the Dark Brotherhood. Horse theft is also a non-starter as horses can't be sold and stolen ones will wander off as soon as you dismount.
The main problem with being a thief is that if you haven't got The Skeleton Key yet you will have to take the cost of lockpicks off your profit margins. You also need to gain access to a fence to actually sell the stolen goods to – but you should do this anyway. The willingness of a fence to buy stolen goods is nothing compared to their real virtue: they will buy any type of item. If you have Mercantile of less than 50 this will save a lot of trekking around between stores. Fellow Chronic Fatigue sufferer Ongar also does business 24 hours a day!
Adventurer
The presumed default livelihood for a player character, this method of making money entails exploring the world at random. If anything attacks you you kill and loot it. An aspiring hunter can also shoot harmless deer for Venison. If you find a ruin, fort or cave you go in and scour every inch for valuables.
This method can produce excellent results but the rewards are highly variable. Slain beasts and monsters rarely have much beyond a single pelt or alchemy ingredient whilst humanoid opponents will have little beyond the gear they have equipped. Weapons and armour have relatively poor gold to weight ratios so you'll soon have to head back to a merchant. This questing is all about the occasional rich find such as an enchanted item, although at higher levels you'll lament the fact that no single item can ever be sold for more than 3000 gold.
The biggest problem you'll face is that avoiding death and slaying foes requires the expenditure of potions and enchantment charges as well as inflicting wear on your gear. Less profitable expeditions can see the proceeds eaten up by these expenses.
Energy Drink Salesman
Alchemy is a great way to boost the sale value of applicable items. Combining ingredients will usually produce a potion or poison more valuable than the ingredients themselves. You can even 'launder' stolen ingredients into a potion that is legally yours.
The main limiting factor on Alchemy is that you need to combine different ingredients with the same unlocked effect. Fortunately almost every kind of food has Restore Fatigue as the first effect listed. Such food ingredients are cheap or free and exist in over 20 different common forms. This means that making money from Alchemy mostly consists of making large numbers of Restore Fatigue potions and offloading them to a vendor in the largest batches they can pay for.
Hero of Cropsford
A family is trying to build a new farm at Cropsford, only to find that it is currently the battlefront of a war between two goblin tribes. If you can solve these zoning issues they actually build the farm over the next in-game month. After full completion the larger house will have a Reward Chest upstairs. Once a week the family will deposit around 10x your level of gold in it just for you. It isn't much, but passive income is no small thing in Cyrodiil.
Mages Guild Member
None of the organisations available in Cyrodiil offer steady weekly work to the PC until they are at the top of the hierarchy. Instead each offers a quest chain of one-off jobs. The Mages Guild are the worst at compensating you for these efforts with actual coin – which is to say they never do. It seems that the majority of the Guild make money by trading, training or teaching spells they've managed to invent with the University resources.
This culture persists even when you are Archmage. There is no salary or benefits except that you can use a magical chest in your new private quarters. This provides 10 duplicates of an ingredient you already possess once a week, augmenting your existing Alchemy hustle or providing a modest sales income.
This picture changes significantly if you become a Fake Vampire Hunter. If you get in with them the right way the Order of the Virtuous Blood will pay 250 gold per Vampire Dust delivered. An unscrupulous Archmage can therefore relieve them of 2500 gold per week without actually risking contact with a vampire.
Unlike the Fighters Guild, the Mages Guild actually has items of reasonable value lying around everywhere that you can take once you've joined. The only downside of this is that the Guilds look a lot less nice without their set dressing. If you are planning on visiting often (for example via the portals in Frostcrag Spire) you may come to regret giving these places a post-plague-of-locusts look.
Arena Fighter
The Arena will employ anyone who wanders in off the street if they can withstand the abrasive greeting they will receive. Successful applicants are invited to to go and fight a candidate with a similar number of Arena wins to the death. Considering the mortality rate the rewards are absurdly small, starting at only 50 gold for your first few wins. The money isn't levelled so many players do this quest line early. You can at least get the work done quickly – just walk up one corridor, commit murder, return and get paid. Repeat as often as you can handle for the 12 hours the Arena is open. Once you become Grand Champion you are instead tasked with levelled monster fights for levelled gold but limited to one bout per week.
The main issue with this job (aside from the dystopian slaughter) is the same as Adventuring. Resource use such as potions and weapon charges and any wear on your gear cuts down on the profits. Thanks to a cast iron rule against looting fallen opponents you won't even be getting arrows back.
Fighters Guild Member
The dismal inability of the Fighters Guild to provide employment or equipment for its membership is half the plot of their quest line. At least they generally pay a low but levelled fee for jobs done and you'll always have a quest to do until you become Guild Master.
As Master you will receive a cut of the Guild's proceeds. This is a random amount of gold from 0 to 990 with a a small chance of receiving a magic item (or up to 3 if you focus on Recruitment at the cost of halving your gold). The main issue is that the payout is only made monthly and has no prompt, so good luck remembering when to check the chest. The fact you can potentially get 0 gold and no item when the month ticks over is the icing on that cake.
Thieves Guild Member
The Thieves Guild make it clear that they expect you to work as an independent thief and simply provide the means to sell the results and reduce any bounty costs you incur. That said they have a quest chain of 'special jobs' if you use these services enough. Once you get settled in helping out with these they pay good money for services rendered.
Becoming the Guildmaster doesn't come with any kind of regular passive take from the membership although you do get private quarters. Judicious use of certain Guildmaster-only options can however make you pretty much immune to bounties and even Infamy for crimes if you are able to run fast enough. Encumbrance is henceforth the only real limit on your crime sprees.
Dark Brotherhood Member
The Dark Brotherhood prefer to compensate members with magic items (which are themselves valuable) but when they do pay gold for their hits the amount is relatively high. It is worth noting that their quest chain is unique in having a two-tier reward scheme – completing a kill in a mediocre fashion will see you forfeit the 'bonus' portion of your payment. If you want to make bank with these people you'll need to bring your best.
Once you become Listener of the Brotherhood your role changes. Performing a simple non-combat task once per week will net you a standard cut of 200 gold. This is much less than even the Archmage or Arena Grand Champion can earn from their roles (although it is much safer than the latter). Coordinating a murder cult is clearly a religious vocation first and a money spinner second.
Master of the Crimson Scars
If you want a more mercenary approach to these activities you can recruit the Dark Minion as an Upgrade to the Deepscorn Hollow lair. He can be sent out to murder, returning 2 days later and immediately being ready for another trip if you are there to greet him. He will dare to return even if he fails you (a 25% chance) and tracks suspicion back to you so ineptly that his kills give you Infamy. Despite these failings he will bring back levelled gold on a success and has a 10-25% chance each of depositing 8 different types of loot in a special chest. If you don't care about your reputation with the righteous this is likely to be a far more profitable alternative to managing the entire Fighters Guild.
Captain of the Black Flag
The landlocked pirate ship in Dunbarrow Cove can be filled with useful employees for a fixed total cost of 5500 gold once you've cleared it out. As you bring people in regular pirates will also join your 'crew' despite the total lack of seaworthiness. A full crew of pirates can be sent out to plunder, returning in one week and requiring a day of rest before going out again. They bring back gold equal to 100x your level every time, meaning that this home base can actually turn a profit relatively quickly. Even better you will receive a prompt when they return wherever you are in the world, making them the most user-friendly of all the timed income sources in this list. The only reason not to claim this place at the earliest possible opportunity is that the current residents are actually a challenge for a low level character and will kill you if you are reckless or poorly armed.
Protector of the Isles
After completing the main quest line of the Shivering Isles you will have the duties of Protector. When you enquire with the Chamberlain whilst in the Palace, there is a 50% chance that he will inform you of an attack. You can then either take the matter up personally or command that the guards handle it. When you next travel to the settlement in question you will either face a fight or see your guards leaving victorious. You can then collect a levelled gold reward. Although the reward is higher for personal intervention the fact that your guards always win makes this an effortless way of gaining gold once you've got every settlement open to fast travel. Since the Isles are far too chaotic to be limited to one incident per week, you can basically get as much money as you want with minimal waiting before heading back to Nirn to spend it. This is therefore the best way to make money in Oblivion with the exception of...
Console Commander/Glitch Farmer
In the original form of Oblivion, PC users could open the command console and enter codes. Entering the code additem F (number) after clicking on the player character in third person would add that number of gold to the character. The console commands are different in the Remastered version due to using a different engine but some version of this wealth spawning may exist.
Bethesda games are
famed for their glitches and new ones to exploit are being found all
the time. Some can be exploited in a sequence to take as much gold as
you like.
Neither of these methods are 'in universe' ways to get
money – but if you just want to skip the grind on your latest
character these methods will get you that upgraded house straight
away.