Getting a relatively trouble free unit entails due diligence on your part which includes but is not limited to a careful pre purchase inspection of EVERYTHING and making doibly sure the selling dealer fixes all the issues prior to you taking delivery. Leave no stone unturned.
Far as water damage down the road, it don't ever have to happen if you maintain the caulk and seals and store the unit in the off season in a protected enclosure, or cover it with a suitable tarp or cover when not in use.
Hard items like hot water heaters and fridges and ac units and furnaces require additional maintenance and do wear out eventually.
My present unit has been basically trouble free but I was careful about one, the brand I bought, two, my pre delivery inspection and correction of any issues and three, continuing maintenance.
Keep in mind always that the more complex a unit is, the more issues can arise. Things like electronic entertainment centers, fireplaces, electric awnings and zoned ac can all fail and eventually will.
Myself, I take it as camping so I leave the 'convenience' stuff at home. My units are basic, no frills units. It's camping, not condo living on wheels.
2015 Backpack SS1500
1997 Ford 7.3 OBS 4x4 CC LB