Purchased a 15 year old MH in excellent shape with 36k miles on it with new tires and batteries, and no leaks. BUT it is 15 years old and I dropped $3,200 for total preventive maintenance. Remember I said it was in good shape. It is a 23 foot Class C with a V10. One thing I have learned about MH's is everything gets way more expensive the bigger and older they are. Read all the blogs on here before you buy, great lessons.
I replaced shocks with HD Bilstein's, serpentine belt, flushed engine and radiator, clean mass airflow sensor, installed Ingalls Engineering caster/camber kit, all new cooling hoses including heater hoses and filters, and alignment. That was the list I gave them, they found bad tie rod ends and leaky rear end seal, and cleaned rear end and new oil. I've since had the breaks flushed and new front break hoses installed, and a new high profile Dometic 320 toilet installed.
I changed the converter from a single stage to a three stage converter. I added a dash camera, and in the process of installing two backup cameras. One to feed my GPS and one to feed monitor on rear view mirror. This is all in the first year of ownership. This is my second MH, and five TT, with one still in the driveway.
Sounds outrageous, but at 70 with some physical limitations , I don't want to find myself stuck on the road, worth it to me. Plan on keeping some money back for repairs.