I very much agree that you need to join the RV Consumer Group
and study the information that they supply to new members. It is not easy to buy a used RV and to know that you are getting a good one if you do not have a great deal of experience. An RV is a very complicated thing and there are many things that can be difficult to determine the condition of. They also require maintenance and repairs and that can be very expensive if you do not know how to do much of it yourself. My first advice is that you need to slow down and take the time to learn about RVs first.
You need to know how to make sure that each appliance works properly and that all parts of it are in good condition. RV appliances are very different than those in a house or apartment. They are designed to use 12V power to operate the controls, water pump, and the lights. Other things such as the microwave will require 120V power from an RV park or a generator set. The refrigerator is cooled by heat from either burning propane gas or from electric heaters.
RVs have a plumbing system that is similar, but different from a house. They have a fresh water tank to supply a 12V pump so that you have water when traveling. They have holding tanks for the waste water from the sinks and shower, called gray water and one for the toilet, called black water. The owner needs to know how to use, care for and maintain all of these systems.
There is outside maintenance that needs to be done and if you buy used, you need to know how to tell if it has been done as needed in the past. Remember that tires need to be replaced at least every seven years, no matter how good they look. Trailer tires that are older than that are just blow-outs that are seeking a place to happen.
There is much more to know and the more that you learn before you shop the more likely that you will find a good RV to buy.