The breakdown between the "Park" price and the "Homes" price is arbitrary ... until it isn't. You can't really figure on buying a park with a lot of POH for 20% down on the whole purchase price because the homes "drag" your LTV down (since no-one will lend on the homes as collateral).
Who decides the price and who decides if you can get your POH "for free?" It's up to you and the seller, so long as the bank (appraiser) agrees. But be careful about splitting things up differently for different people (you, Seller, Lender, County property tax & recording deed fee (based on recorded value of "real" property). Different parties have an incentive to push your allocations of purchase price in different directions.
IMO It's best to be realistic about it and realize that 80% LTV on the whole deal is probably unrealistic (overleveraged) and plan for more cash "down" as a percentage of the whole deal price - I figure generally that 2/3 of the purchase price can probably be financed. If you assume 70% then you need to come out of pocket $390,000 on this deal, not $260,000. That's maybe broken down $100k homes, $50k startup costs, $240k down on a "theoretical" loan on $1.2mm at 80% ($960k) but that is really a $340,000 down and a loan of 960k ($1300-340).
You can swing the numbers around a little, but my point is this: a "quick-and-dirty" calculation of how much "park you can afford" is 3x or 3.5x your available cash for investment, not 5x your cash.