https://nrvia.org/ They have the skills and TOOLS necessary to do a full inspection. I spoke with a couple inspectors near one rig I was contemplating, and it was surprisingly affordable, especially as it would have been an out-of-state purchase for me. I wasn't willing to spend the money on plane tix, rental car, hotel and meals, not to mention lost income, just to find there was an issue. Now, if it's a local buy, and you feel that you have the skills/knowledge/tools to do the job, and risk the money you'd spend on an inspector if you miss something, then go for it. These guys are pros and are putting their reputations and jobs on the line to give an accurate report. Also, they can actually help a =seller= either catch a problem that they might not know about or tell the seller that what they =think= is a problem, actually isn't. If you'd hire a home inspector, why not for an RV? I have no connection to NRVIA, nor have I had a chance to use one...yet, but I certainly will, if/when that time comes.
Lyle