So if I don't have a bank appraisal how to get the board to lower the taxable value? 

However, it would seem your pool of buyers gets decreased a bit by going this route.

That said there may be a small bump in first time homebuyers due to a decreased down payment requirement.

You can ask the seller to pay closing costs - decreasing your payments a little more.

Seems he said he avoids the Southeast parks.The reason I brought this up was because I was noticing that many, if not most, of the MHP's for sales in the Southeast were in areas of decreasing population and/or areas with a declining general outlook with regards to jobs, industry, population growth, etc.

Just buy a federal tax free Muni (5.6 taxable equivalent) with the 420k and rent if we decide to go the high school route?

Actually, if the property has been held as a rental property and you move into it, the gain will be allocated between the number of years that you have rented it out vs. the number of years that you have lived there in order to determine the amount of the gain that will be taxable vs. the amount of the gain that will be tax-free under Section 121 of the IRC. 

I am comparing it to a taxable brokerage account (since I already max my 401k and IRAs) which would receive the same base and injections. 

It usually decreases by a couple of points short term.

HOAs decrease flexibility of creative financing.2. $200 a month Pos Cash Flow is not great.3. 10% down is alot to buy, I buy on sub2, wrap and lease option assignment.4.