My wife and I bought a 1998 Four Winds 5000 23rk with 36,000 miles last September. The MH is 15 years old in excellent condition, but it is 15 years old. I have owned an older MH before, a 1978 I bought in 1992 with 50K on it and Chevy 350. Never failed me and I did all my own repairs and up-keep.
I took the Four Winds out on a 300 mile check ride through Yellowstone and Grand Teton Parks and it preformed well. But, I know the heater and radiator hoses and belt are most likely 15 years old and the things most likely to quit on the road.
Because of age and health issues, I am going to have them replaced this spring. The next thing will be the shocks then alignment. The tires are all new except for the spare which I will replace with a new tire. Of course, regular fluid checks and changes. The MH is garaged unless on the road. Hope this gives you some ideas about keeping and older unit well-maintained. I'll have peace of mind and know the condition of the MH when done.
As far as the house and electrical, expect something to give problems, but it is all repairable. The way my wife and I look at it, is, if the engine blows up and we replace it, we are way farther ahead then a the bloated price of a new MH. But I doubt that will happen. Owning a motor home is expensive, they seem to surprise one at times with a glitch, just as the new ones do. Good luck, and good roads.