I took the inspection course, which was a good overview of RV systems. It helped a lot because I do most of my own work and it saved me from making a some dumb mistakes.
After you pass all the mastery tests, you get an NRVIA emblem to put on your business cards. I dropped a few off at the local RV shop (the shop is so busy he doesn't have time for inspections) and throw him $50 for a referral. I think I've done 2 inspections and a bunch of "I just bought this motor home and don't know anything about motor homes" jobs.
BTW, if you join the inspection connection network, they charge something like $1300 for an inspection and you get half. All they really do is act as a referral service. No one is going to pay $1300 for an inspection.