7 year old trailer will have almost all the same parts as any other trailer of that same generation if the manufacturer is still in business or not.
If you are concerned about getting it serviced, then check (first before buying) with a couple RV dealerships in your area about servicing this specific brand and year of trailer. They also may be able to look up information on the camper you do not have access to and can let you know if their service department can (is able to) do the mechanical repairs you may need.
Probably 90% of the trailer can be serviced by any RV repair shop. The other 10% will probably have to be customized somehow. But for the most part, all camper are is a wooden or aluminum box on wheels. The frame, the tires, the propane tanks, the stove, the refrigerator, the battery, the lights, the radio, the furnace, the water heater, the holding tanks, all of that, faucets, fixtures, flooring, matters can be swapped easily if a repair shop has some real seasoned mechanics and know what they are doing.
If the price was right, I would not have any concern about purchasing a trailer 7 years old, even if the manufacturer did not exist any more. Here in Indiana (at least), the competition is everywhere, and every dealer-repair shop I've had business with, gladly works on all brands of campers.
Repair shops only have a hesitancy when the camper is being repair under WARRANTY! Big difference if you are attempting to get a repair from a dealer under warranty or if you are paying for the repair yourself. They will not tell you "no" if you are paying yourself.
Off topic a little, my son bought a used PT Cruiser from a Chevy dealer. The Chevy dealer serviced his car for 3 years, and then one day he decided to take the car to a Chrysler dealer for the next repair (brakes I think it was). Either dealer gladly worked on the car because my son was paying with cash (or credit card), but not at the expense of the manufacturer. A volkswagon dealer will repair that PT Cruiser if he took it there! They won't say no. It's revenue for them, paying cash, and not having to deal with warranty strangleholds!
Same is true for RV's. YOU PAY for the repair, and they will do it! So don't feel you'll be left out in the cold looking for a repair shop if you need one.
About the condition of the camper itself. You need to check it completely, top to bottom, inside-out, and front-to-back with a tooth-brush and a q-tip! If it's well maintained, you'll know that immediately. If it's junk cover-up, you'll find that too. A 7 year old camper "should" still be in good shape if it's never been wrecked, had a limb tear the roof, or simply been neglected and gone through a tornado or something.