If you are considering a 5er and truck, you really need to do lots of research and become VERY familiar with both the truck and trailer's weight ratings. Don't be misguided by the "dry" weights as they are pretty much irrelevant. Pay close attention to the truck's payload capacity, RAWR, GVWR, and GCVWR. The trailer's main concerns are the pin/tongue weight (again forget "dry" weights) and its GVWR.
For quick estimations, use 20% of the 5er's GVWR for pin weight or 15% of a travel trailer's GVWR for tongue weight. For the truck, make sure you have about 1000 lbs of payload left over "after" the trailer is hooked up.... for you, passengers, tools, equipment, hitch, etc.
For instance, if you find a 5er that has a GVWR of say...14,000 lbs, take 20% of that (2800 lbs) for the pin weight. That means that the truck that you will need to pull it, will need to have a payload capacity of about 3800 lbs.
Don't go into a purchase until you are very confident that you understand all of the above. Don't listen to the salesmen when they tell you "this is ok, your truck will pull this", as they just want to make more on their commission.
Be educated, be smart.
Good luck
Ron