My rule of thumb is to expect to spend 10% of the purchase price the first year to get things right.
Your estimate for tires (assuming 6 not 8) is high. I think $2500 would cover it, unless you insist on Michelins.
You should be able to get 4 Trojan 105 6 volt batteries for less than a thousand, and these are probably the most expensive batteries in the bunch.
Most of us that own older coaches are able and willing to do the work ourselves. If you can and are, you'll spend about half your estimate for things like roof repair and flooring.
