The most common limiting factors you will find in finding a TT suitable to FT in are:
1. Not enough carrying capacity (low CCC) - Most FTing couples recommend 3,000lbs and up. Finding storage space to put 3,000 lbs of gear is a limiting factor too.
2. Poor insulation - look for upgraded insulation packages with thermal foil. heated holding tanks, an insulated compartment for valves, and double pane windows if possible.
3. Weight (and possibly tongue wt.) will be a limiting factor also, depending on what kind of TV you have. For a TT I recommend no less than a 3/4 ton, and a diesel if you can afford it.
If money is no object there are custom TT manufacturers, like Spacecraft, but their units are pricy even used, and some are very heavy, requiring a huge TV.
http://www.spacecraftmfg.com/
If you are looking for something more affordable I would recommend the Highland Ridge Open Range models http://www.highlandridgerv.com/journeyer/floorplans.php
I also like the Keystone Sprinter line for more affordable, yet decent quality trailers. http://www.highlandridgerv.com/journeyer/floorplans.php
Be sure and look at toy haulers too. I like the Work and Play line by Forest River as they are lighter, have good carrying capacities and a metal roof that won't need replacing every 12-20 years like EDPM roofs do. Here's my favorite model, the 36FKBS with a center bedroom and 2 slides, though it is a little on the heavy side, it is well made. http://www.dreamchasersrv.com/rv/WORK-AND-PLAY-36FKBS-TH0015241
Chip
1999 National Tropical
Triton V10, Ford F53 Chassis