If you have no qualms with stealing and/or knocking out people while they sleep, you're in luck! Did you know that the gamblers at every tavern carry around 100g on them, and the main gambler you can play dice with carries anywhere between 300-1000g? Yep, there is just that much gold lying around in the easily accessible pockets of sleeping villagers every night and in every village, and it will require basically no skill or leveling to take it from them.

Just wait til late at night, usually around 11pm-midnight, and everyone in the tavern will be asleep. You can sneak around and knock everyone out (it's completely silent) and pick their pockets. All of the gamblers sleep in or around the inns where they gamble during the day, including the one you can play with who has the most money on him. Gamblers will just be called "Villager", so you may have to do a little fishing around to find the guys you want.

I made >2k in two in-game days by travelling between Talmberg and the Inn at the Glade, literally the day I woke up in Rattay for the first time in the main quest. Got a Lvl 5 horse a day later.

Happy hunting!

BIG NOTE: I discovered this while playing in hardcore mode. Some of the prices and such are different in hardcore mode vs normal mode, so there may be more or less money on them in normal mode. I'll update this when I've confirmed the relative amounts in normal mode.