Next to Ghost Hideout you will see a purple flower called Comet Bloom this can be picked & then if you enter Ghost Hideout & leave it will re-spawn you can collect as many as you see fit. These can then be sold to any trader for $65 but the trick is that you can buy them back from the trader for $45 leaving you with $20 profit. I harvested 25 x Comet Blooms and use this glitch to make a nice $500 per transaction.
There is a limit of $9999 cash I understand but I usually just keep a few thousand dollars in my pocket in case I find any new weapons or schematics
Then time to go shopping for Ammo & Wingsticks
Alternatively you could play any of the mini games to make some cash but after a while they begin to bore me & I much rather have a fat wallet of cash & explore the wasteland to see what I can find.