Yearly routine costs can vary, depending on how old the unit is, all the different things you have on it and how often you drive it. You may not need to replace the tires, but every 5 years, but if you have 6 of them, it could cost you anywhere from $1500 - 3000+ for new ones. If it's an older MH, you've got to count in things that will eventually fail and need replacing.
My father in law had a Monaco 42 or 45' DP a few years ago that they bought new in 2004 I think it was. He told me at one point it was costing around $10,000 a year to keep it going. The unit was paid for, but he was talking about costs in maintenance, repairs and etc. Not sure if he was talking about taxes and insurance also, but could of been. Of course that could of been one year that he was talking about he spent. But you never know.