It does seem a bit high -- I have seen 2007 8357I models for little more than that price with as few as 5K miles on them. Nationally, the lowest prices seem to be in Florida where you are, so bargain that one down or keep looking.
When you say "last for 10 years" it heavily depends on how you intend to use it...will this be a vacation vehicle of just a few weeks a year or a full time home? Will you put 3,000 a year on the coach or 30,000?
If you will be putting a lot of miles on the motorhome or towing anything more than 4,000 pounds, consider a diesel. All these rigs will need ongoing care and maintenance, so factor that in as well.
2007 Tour Master T40C
Acura MDX toad
"It takes a great deal of time to recover from any improvement..."