Here's a tip I have:
If you find yourself in a bind with no money, no supplies and no fuel, and you have already liquidated all your exess assets like guns (I have found myself in this situation often lately), your crew are a great untapped resource.
I hit up a black market and sold all of my elite crew (sorry homies), to replace them with greenies (they'll level up), as well as enough left over money to restock so I could get a nearby bounty and get out of the hole I had slowly dug for myself.