Just be mindful that the demand for RV's is high and people are asking (and getting) premium prices for their used rigs. It will be hard to assess a good price for a used RV because many buyers know that if you don't buy it, there will be others behind you that will. So, harder to negotiate prices. And harder to determine what fair market value is as well.
You can try using things like NADA and look at their used values for any RV you are looking at. Just be mindful that their values are most assuredly pre-covid, and RV prices are in territory that really no one can accurately evaluate. But, it will still give you an idea if the seller is insane, or just a little crazy in their valuation.
I read your other post as well about getting into RVIng for first time, and maybe doing some full time RVing as you look for a new house. I don't know how the RV rental market is in Canada, but you might consider renting as you work the bugs out of your RVing experience. Renting an RV can give you some time to figure out what you like about the particular rig you are renting, but more importantly, what you DON'T like. So, when you get ready to buy, you know what's important to you and what you're willing to compromise on.
Obviously, renting an RV is "sunk money" that you won't get back, but it could better prepare you for this big step. Plus, give you some insight and thoughts about what to look for problem wise in RV's. The suggestion about hiring a mobile tech to evaluate/do the PDI is a good one too.
Just food for thought.
Mike