First off what do you have for a TV? If you don't have an adequate TV a TT won't do you much good or you have to buy one. Before looking at anything you need to decide what type of use is going to occur, FT, weekends, 2 week trips, etc. I would read the forum on pre-purchase checklists, what to look for, manufacturer issues, etc. Do as much homework as you can and educate yourself before you go look. If you have specific questions then ask. You also need to let us know what type of budget you have. Because then we can give you specific information on what to look for.
I could give you over an hour on things to look at before you even test drive a rig or look at a TT. Repairs depend on how handy you are and can you work on engines or not. Figure anything used will require as little as $1000 up to $mega dollars. I've spent about $1500 on my 03 Chateau (which was in great shape) and as much as $3000 on my 87 Allegro that I sold last year. Some have spent less and some much more.
The key is education before you begin to look.
2017 Grand Design Reflection 303 RLS
1997 GMC Sierra 3500 Dually