Buyer will miss on deal after deal..

I have been using the tools learning tools BiggerPockets provides to find deals and analyze deals. 

Most important is to find the best deal possible, if you find a great deal there are always partners for that project.2.

By the way, I had no idea that there were so many non recourse lenders on smaller deals. 

My parents who invest, say they never do deals with more than 15 year amortization.

I am currently considering a deal on a very small park as a way to test if MHP's are going to be for me or not.

Sounds like you need to sell one or two, or you can do a HELOC (check more than one lender on HELOCs on them) to value add the deals (ADU, and or buy another property to cashflow). 

About to close a deal all cash for $1.46M and was going to get a cash out refi after to take out about $630K in cash.

He "doesn't want to scare off his tenants if the deal falls through." 

However if are dead set on Owner Financing, you have to get get 20% plus down payment and if you are in Florida, you have to deal with a Judicial foreclosure process which is not nice to Lenders, I would highly recommend against it.