I did it in the earlier versions by restarting until I get sub-quests I could actually finish. Then it's matter of not over-spending. The recent version should be even easier to make money, since you can just sell the slaves you got from dungeon for a sizable profit each run (anywhere from 100 - 900). Even if you're unlucky with the drop, you still shouldn't have to spend more than 3 trips to pass the first 1000 (Goblin dungeons are recommend, since they're the easiest one). The 3000 can be bypassed with certain privilege that comes with advancing the main questline, or you can just pay them still; your combat party will have become strong enough to make several trips without resting by that point.