There is a bandit hideout near Whiterun (NW). The enemies in there may come at you en mass (small cave), so caution is advised. Inside there you can find the spell tome: 'Trasmute'. That spell turns one iron ore to one silver ore, or one silver ore to one gold ore (just ores, not ingots). Plenty of iron ore in that cave too. In fact all iron mines become, essentially, gold mines. Even someone who has a low alteration skill and has taken no magicka increases, can cast the spell.
I turn all of my iron ore to gold ore, and then make ingots. After that I make jewelry (gold rings, unless I have gems for something better) at the forge. Not only does it raise my smithing, but I have plenty of gold rings to sell. If you can add a magical effect to the rings, all the better.
My instictive reaction was how to make money from an honest day's work (alchemy turns flowers into gold) until I realized how silly that is.
My advice is to walk from one major city to another and explore a couple locations that you find along the way. Honestly, I left Whiterun a little below 10th level with only 300 gold. After a few in-city quests in Windhelm, I walked back to Whiterun and returned with enough money to buy and furnish Breezehome. I think most of my money came from a dead dragon, malachite mining in Kynesgrove, and a couple forts that I explored while heading home.
A separate character probably bought Southside Manor in Solitude with the money made from a few random dungeon crawls. It's a little crazy how fast money can accumulate.
After you get this, mine some iron, collect some pelts, and smith iron daggers. Sharpen the daggers, and then enchant them with Damage Stamina. Watch the money roll in. Happy money-making, John! :D If you buy the ingots pre-made, or the leather pre-made, you will more than likely be operating at a loss.
Or find a quest bug which gives you infinite gold lol.
I found one in Blood on the Ice the other day (didn't use it much since I have 100k+ in my inventory and chests full of stuff I could sell if I need more).
To exploit it... When you have the option to give the amulet to old make from the hall of oddities or whatever, do it, he'll give you 500 gold. Then pickpocket the amulet back. The dialogue option appears again. If you use it again he'll give you another 500 gold. Keep it up for however long you want.
Another exploit is to find somewhere where the guards (or someone like the guy in the thieves guild) are practicing archery. They have infinite arrows. So go and take them from the target. You can now go and sell the arrows, come back and take some more. Also you can reverse pickpocket better arrows into their inventory and make more money, or a source for an infinite number of better arrows for you to use.
Another trick is to save the money you have. I was tempted to spend my money on training early in the game. But then thought I should pickpocket my money back. Soon found the trick to be that your pickpocket chance depends on the value of what you're taking. So if you train 5 levels then try to pickpocket you'll be out of luck (0% chance to steal), but if you train 1 level, take your money back, train 1 level...
the best one i can think of is to go to halted stream camp north of whiterun. there you will find the spell tome: Transmute Mineral ore. this dungeon has a large amount of iron ore. mine it and use the spell to make gold ore. once you have the ore go to whiterun and smelt the gold ore. use the gold ingots to make gold rings. enchant them in dragons reach and you'll end up with around eighty gold rings that can sell about 400-800 gold coins. you'll be set for pretty much the rest of the game, hope this helps.