My approach has been to make the widest possible survey of options out there. Then identify one which seems to meet your criteria and PRETEND that you bought it. Live with it in your mind while you check availability and prices. If it still seems like a good idea, decide on the model, options and price you are willing to pay. Then start monitoring Craigslist, etc. every day until the right deal presents itself. Once you find it, jump on it (it won't last long). Don't be afraid to travel to get it, but watch out for rust from Southern/Eastern states.
Hopefully, you will be able to leapfrog some of the steps on your RV journey.