There are a few decent guides on money making here already:
Making Money Without Crafting, Cheating, Or Exploits | Skyrim Forums
How To Get Money ( ALL WAYS ) | Skyrim Forums
100,000 Gold | Skyrim Forums
The end of the Dark Brotherhood questline gives you 20,000 gold, but you'll probably make enough gold during the course of the questline to buy a house.
A lot of the quest gold rewards are level dependent, so when you're lower level you get less gold, and if you did the same quest at a much higher level you might get 5x more gold for it.
Don't know what kind of character you're playing, but you can join the Thieves Guild and progress up until you can sell things to the fence there, Tonilia. She buys stolen items, so you can go to an Alchemist's shop and steal all the very expensive and very low weight potions they have on display on shelves. Then you can go sell them all to Tonilia.
You can make and sell expensive potions with Wheat + Giant's Toe, Blue Butterfly Wing + Blue Mountain Flower, Deathbell + Salt Pile, Canis Root + Swamp Fungal Pod, to name a few expensive potions with easy to obtain ingredients.
You can make, find or buy Iron Daggers, and enchant them with your most expensive enchantment, even with petty gems you will make some quick gold.
And finally, a cheating way to get very quick gold. There is a hidden chest in Dawnstar that belongs to the Khajiit caravan that comes through. It has the sale inventory of the caravan for you to access and take for free, then sell at your convenience. If you want to use this method, search YouTube for Dawnstar Chest, I won't post it in here in case you don't want to know about it.
