Lots of things to consider. Budget? What will the vehicle be used for when not towing, if anything? How big of a toad do you need? How bad do you want another vehicle around and have expense of license, storage, insurance? Do you have a vehicle now that can be modified for towing? Are you planning to flat tow or tow using a dolly? How close do you want to push your GCVW limit? Whatever you tow, you really should have a brake system (required in many states). If you don't overload your RV, you probably have capacity to tow up to 5,000 with a typical class C, but in my opinion I would try to keep the weight of the toad around 3,000# or less.
A good resource for vehicles that can be towed, and what restrictions if any can be found at http://towingworld.com/resources/2015DinghyGuide.pdf