Steve, I'd suggest that you slow down a bit and work at your "mission plan." You have done part of the work, in that you know that a towable is your best bet. Now, think a bit more about how you will be using your coach. You said that you will have a home base at your sister's place. Have you checked into the zoning laws for that? If your idea isn't permitted, do you have a Plan B?
When you are traveling, where will you go? When you are at home, what's the climate like? Few, if any, coaches are intended for extreme temperatures. If you will be facing temperatures below freezing you will need a coach that has heated tanks. If the below freezing temperatures will be for several days you will probably need to either insulate the space below the coach or add supplemental heat. Either way you will be looking at using a LOT of propane. If you are looking at temperatures in the high 90's or above you will want a light-colored coach with at least two air conditioners. That means 50A electrical service. Your sister will notice a great increase in her electrical bill.
What sort of truck do you have for towing? Coaches that are intended for full-time use are heavy. Sales people will tell you that a 3/4 ton truck will tow anything, and they are right - to a point. Nearly anything can drag a trailer down the road, but stopping it SAFELY is another matter. You are better off having more truck than you need than too little.
The empty weight of the coach is a good first number to have, but it isn't the most important one. GROSS weight of the coach is much more important. That's what the coach will actually weigh when you are going down the road.
Mercury Mountaineer towing mpg 181(both sold)
1993 Foretravel U300 40'