This thread has taken some interesting detours to be sure.
Re the mobile home... Do you own the land or are you paying space rent in a mobile home park? If it’s the latter, you do need to consider yourself still a renter without long-term housing security. If you own the land, you have the security of a permanent place to come back to- a place to spread out, to store stuff, to make repairs on your RV, to obtain health care and recuperate from illness, to maintain friendships and community ties. Those are all good things as you age. The "RV port" concept gives you some of the same benefits, but it seems you like living in the LA area.
So... you're considering an RV for occasional recreational travel. It might be your only vehicle. Is that because of limited parking, cost, or...? If it’s your only vehicle, I’d want something as close to a stock van as possible and as close to 20’ as you can live with. The bigger it is, the less enjoyable it is to drive, especially in the city, with fewer options to park. Routine service and repairs on an oversized vehicle can get complicated and time consuming, and you’ll be without alternate transportation while it’s in the shop.
If you have a second parking spot, you might even consider- dare I say it on a Class B forum?- a small towable RV. They are cheaper to buy and insure, easier to work on, and you don’t have to take your camper to the grocery store. We also have a small fiberglass Scamp trailer, 13’ long tongue to bumper. It’s not self-contained, but they also make a self-contained version with a wet bath (bigger than the one in my Roadtrek). It can be towed by a small pickup or even a number of compact SUVs. Insurance is around $130/year (and not required at all unless you want full coverage) versus $850/year for the Roadtrek.
Before you do any of this, you might consider renting an RV. Since you’re “not a camper” by your own admission, it would be nice to find out if it's even something you will enjoy before taking the ownership plunge. It will also help you determine what size RV you really need.