What APT said, times 2 !!!
Various manufacturers have varrying reputations. Rockwood (Forest River) has a fairly good following, however, the manufacturers involvement pretty much ends with the initial warranty period. If the unit is not well maintained, it will turn into junk, no matter who put it together. The electrical, plumbing, frame, brakes, tires, appliances, etc, are pretty much common with all the manufacturers.
Even though the unit has very little milage, if the tires are original, they should be replaced. If the wheel bearings have not been serviced, they should be done. If the battery is original, it's about due.
Signs of leakage can be soft spots and / or stains in the floor, walls, and ceiling, along with a mildew smell. Look in every space (cabinets, closets, storage comparments, behind the toilet, under sinks, around the shower), anywhere your head and a flashlight will fit. Check the roof for cracked caulking or tears in the roof membrane.
A common place for leakage are running lights. Water gets behind the lens, fills up the fixture, and leaks inside the wall. Check the lenses for water lines or build up of dirt on the inside of the lens.
On the exterior look for rusty screw heads. If the head is rusted, the rest of it is probably the same.
Look for wavy wall panels, inside and out.
