I know the ins and outs of construction, I have a great relationship will a wide variety of trades people and I am pretty handy myself.

Comps vary widely on Zillow (I don't have access to MLS...sitting for my agent's license next month).  

I'm in the UK but the technique will be the same world wide i would have thought.

The caretaker had bought his own double wide MH and put it on our property..

When you're ready to get started, wait for the right deal, run it by your mentor and make sure you have a wide margin of safety.  

I  went  back one  month, county wide and there not many records.

In Lufkin a dealer has this ad up for a New MH for $40K , delivered (but not set up)http://nacogdoches.craigslist.org/reb/5405774303.h...In my area a new Single Wide set up is running over $50K.If the Mobile's are less than 10 years old, you might not have that many problems.  8-12 years are when Water Heaters start to fail, and MH Water Heaters can cost more than regular ones.  

There is a wide range of knowledge and professionalism between agents, and you might have to go through some to find the one that you like.  

If the there are no major cracks like 1/4" wide or more, then you most likely you wont see any more cracking in the future. 

Perhaps the buyers will change their minds, perhaps they won't feel you gave them exactly what they wanted, perhaps the market will drop, and if you've done renovations that aren't marketable to a wide segment of buyers, you may have to do a new renovation to resell.If you do move forward as the "builder," I highly recommend you work with a knowledgeable attorney to get a rock-solid contract, get a big deposit, and make sure the numbers work in your favor at all points in the process.