The NRVIA certifies inspectors with an online course and tests and a hands-on inspection at their facility. You do not need the hands-on part to get the NRVIA certified inspector badge for you website or business cards, just to get references from NRVIA.
NRVIA charges something like $1300 for a full class A inspection and the inspector gets half of that. They require the inspectors to get errors and omissions insurance. I've never talked to anyone that would pay $1300 for an inspection. I charge $300 and most people think that's too much. I believe that's what my time and expertise are worth.
I took the courses and the tests, downloaded my badge and that's all I had to do with them. Printed up some business cards and dropped them off at the local RV shop. I give the shop employee that refers me $50. I do 3-6 inspections a year.