This is a hard one to answer, and while I tend to agree about all $10,000 motorhomes needing work, the truth is there may be the occasional gem out there, but by occasional I mean closer to 1 in 100, not 1 in 10 and even these gems may still need some freshening, and are always private party sales.
As to the cost of ownership, there are a lot of variables, the big ones are going to be can you do some / most of your own repairs, and do you have a place to store the coach? The $100 per hour that most RV shops charge for labor can make even simple jobs expensive very quick. On the storage side a lot depends on where you live, if it is open storage, covered storage, etc. Insurance also varies from state to state, but on an older coach you should expect somewhere in the $700 per year ballpark, though it is a big ballpark.
As to my personal experience, last year after 5 or 6 months of shopping I bought a 15 year old small class A last year for $20,000 (total actual out of pocket was a little more as it was a thousand miles away in Florida from a private seller, call it $21,500 with retrieval expenses). Overall I would describe its condition as very good, the previous owner had put over $10,000 worth of parts into it not counting labor since 2014 when they unexpectedly found themselves needing to sell. So not exactly a $10,000 special, still in the first year I spent somewhere around $6,000 on maintenance and upgrades, I have also put about 6,000 miles on the odometer. Out of the $6,000, $1,800 went to professional repair service which included repair of the brakes, the dash air conditioner, and a number of fluids changed. Much of the remainder were small items, like replacing failed marker lights (sockets corroded), ranging up to installing new shock absorbers, and a lot of stuff in between. Of the $6,000 I would say that about $1,000 was needed to be spent for safe operation (fixing the brakes, and replacing a leaking propane regulator, new CO detector ...), $2,500 to make operation much more pleasant (dash air conditioner, shocks, ...) and the rest were upgrades that fell more in the nice but not necessary side, such as adding a SeeLevel 709 tank monitor system, and LED headlights.