I downloaded crossfire two days ago and had a similar experience to dogeddies. When I saw that I needed a couple hundred k to get to the next level, I figured that I would get tons of money for completing combat missions. When I discovered this hadn't changed, I figured I was missing something. To be honest I thought the mod just really wanted people to have to practice trading (before I figured out the prisoner thing).
Anyways, as Skum said, buy a Rhino, do some trading. You can make the money in 15 minutes if you know what to trade and don't feel like exploring.
