We live in a larger/nicer than average home on acreage, have two vehicles, a TT, raising two boys, vacations, saving for retirement, insurances, and on and on...and we do it all on about $7k per month with no debt. I would sure hope that I could make it just the two of us in an RV with the same money!
FWIW, I am 12 years out from retirement and planning to do it with about $3500/mo. plus some work camping. Not sure if it will work, but everything else that I've not been sure of has figured itself out along the way. A large part of making things work is how "adjustable" you are. We're very adjustable...there's been years that we've put a complete lockdown on finances in order to get back to our safe area. Some/most people can't do that.