Andy
Welcome to the world of RVing. I'm assuming you haven't had an RV before.
For those of us in the USA that's about 53,000 miles which is considered low mileage for that age of vehicle.
In answer to your questions... if the vehicle and RVs have been well maintained and no major damage from accidents they will be reliable. The running gear on a trailer will last a longtime with proper maintenance. The stuff inside also should hold up as well as the stuff inside your house does (again with proper maintenance).
Travel Trailers will reach a price plateau of $1500 to $3000(us) as they get older than 10 years; depending on size plus condition. New travel trailers are rarely above $30,000 plus with 15 year loans many folks choose to go new rather than take a chance on used.
One more point, most RV'ers go through 3 to 4 RVs before they finally reach one that meets their needs. Many start off small like you indicate and then move on to progressively larger tow vehicles and RVs.