The best way to pay for you RNG through the lower lvls is to take your high-lvl class out and farm.
The NM idea is great - within certain limits. I take my THF30/RNG15 out and farm in areas where, within widescan range, you have multiple NM/rare mobs appear on a regular basis. Most of these areas also have decent farming, so you can make money the old fashioned way while keeping an eye out for the uber-item.
Most people don't realize how much money you can make harvesting/logging/mining. Yes, you'll break pickaxes, hatchets, and scythes, but you can get a lot of stuff in the meantime. For example, I'll run over to Windhurst with 6 scythes in my hands, and when I've broken the last one I'll have about 15 full or nearly-full stacks of items, some of which are fairly expensive. In ERF, you only need two Elm or Chestnut logs and you've paid for a whole stack of hatchets. Haven't done much mining, but from what I hear it's about the same situation.
"There's a new twist in the game."