As an older canoe and tent camper, I believe you should rent a unit similar to what you want. It is what we did.
It is easy to be overwhelmed by all the features and styles of TTs on the market. However, pulling one of these units down the road has to be experienced to be understood.
A week or 10 days adventure will explain a lot about the size and floor plan you need. It will also give you a feel for the RV life.
The obvious items include 10 mpg, 300 mile days, and tow vehicle size. The less obvious includes maneuvering, parking and maintenance.
Renting teaches you a lot in a short time.
In answer to your question, cost and the suggestions already mentioned are as good a purchasing guide as any.
Good luck and remember buying a TT is not a race.
