Hunting and fishing money
Hunting and fishing are the best ways to make money. Fishing especially. There are a few good fishing spots with fellow fisherman vendors hanging out at the same spot. Get the Fisher King perk, practice some fishing, and once you get the hang of things you can turn around trout and bass fast enough to make $1000 in a couple minutes. Be sure you're using a fly that make sense for the fish you're going after!