I'm so glad to hear of this new adventure you are contemplating, Tom!
I can offer our experiences with a 1976 Airstream Argosy, the motorhome that was based on the trailers. We bought it in 2003 for $9000 and just sold it last summer for around $7000. Though we never lived in it full time, we did a number of extended trips so got to know it pretty well.
I think you are making a wise choice to look at smaller/shorter RVs for your situation. Becoming comfortable with diagnosing and even repairing small problems along the way is inevitable.
Just take it slow and use the resources available online to get help. We actually bought our RV from the air forum site, and could look up all the posts by the prior owner as he did work to it, very handy! Those folks were incredibly helpful when we did uncover problems and various gremlins.
Getting it looked over by the local mechanic is great, and you will want to bird dog him as he does inspections, taking notes if needed.
Outfitting the RV is the fun part, getting it just how you want it, and making the most of your space. I've seen plenty of kitties adjust to life on boats and RVs, and have no doubt yours will be up to sharing the adventure.
Best wishes to you in finding the right one for you.