Hi, Bob -
The price on a 10-year old unit will vary considerably, depending on the condition of the unit, how it is equipped, and the condition of all of its component parts. By parts, I am referring primarily to appliances, which are quite expensive to replace if they have failed. And after 10 years, it is reasonable to expect that one or more may have failed, unless the current owner has been scrupulous about maintaining them. This is true of any RV, not just Trail Manors.
You will find a lot of discussion of valuing older units in the
Prospective Owner Questions forum - I suggest you go through it in some detail. For now, suffice it to say that you should open and close the unit several times to be sure everything fits right. You should try every appliance, in every mode (electric, gas, etc) to be sure they all work. You should plan on replacing all tires (including the spare) even if they have plenty of tread left.
You can also go to the NADA site to find used RV prices, just as you would a car. Go to
http://www.nadaguides.com/
And of course, you will confirm that the running gear has not been submerged in salt water in any of the hurricanes in the last couple years. I think Fernandina Beach was spared most of that, right?
Hope this helps.
Bill