My wife and I figured out some must have and don't want things when we were shopping for our first travel trailer. I was still learning and knew that tongue weight was my limiting factor for our setup. We shopped for a couple of years, going to RV shows and looking at a bunch of used trailers. We found one within our budget, loved it, but we were at our tow vehicle limits and towing sometimes towing was not very nice. We upgraded to a truck from SUV and then started searching for a trailer that met our new needs (kids grown and on their own), again watching CL and local newspaper ads, along with the shows and used trailer lots. Once we settled on which model we wanted, we searched for it, knowing we had to buy used to be in our budget. It took more than a year, but we found it.
Educate yourself, make a list of must have items, floorplan preferences, etc and don't believe everything (sometimes nothing) from RV salesmen and even private sellers.
If you are not mechanical, you need to find a trusted mechanic to help avoid a money pit.