There are issues beyond the FAA "allowing" training. Liability and insurance are a problem for geezers like me with quite a bit to lose. I would need to prove that I could earn enough to cover the additional expenses. I'm not talking about profit, just breaking even. Being based at an airport with a whopping two RVs, (one of them mine) and none in process that I know of, doesn't make for an attractive business plan.
John Clark ATP, CFI
FAA FAAST Team Member
EAA Flight Advisor
RV8 N18U "Sunshine"
KSBA