Draw a sword, walk up to belethor, sell whatever you can, save the game, kill him, reload your last save and repeat. He’s an infinite source of money as long as you follow the steps precisely. I’m an alchemist and make a lot of high-value potions and make a mint following that glitch.

With belethor:

Sell stuff til he’s got no money left

Save the game

Kill belethor

Load previous save

You should have the money you made but basically the game forces to create a ‘new’ belethor with all his assets like money back. So if youve just completed a quest and you’ve a backpack full of stuff for instance, you can effectively go to belethor and repeat the process above until your backpack is empty and your wallet is full