Vermilye's advice is good and information is spot-on, but you may want to "back up a bit" in deciding how you approach the tow vehicle question. Many folks start by purchasing a TT that matches the capacity of their existing proposed tow vehicle. As that isn't an option for you, I encourage you to really work on finding a used vehicle with the capacity to handle a 17' Casita. If you do locate one, it may have such items as a class III hitch receiver and transmission cooler already installed.
While I readily admit that this may require quite a search, it seems to me that the cost for an "adequate" tow vehicle may actually prove less over time than the search, rental costs, and extra insurance costs entailed if a rental source is found.
Either way....good luck.....and welcome to the Casita family!
Edited by nasa42a, 18 May 2015 - 05:19 AM.