The economics of this are pretty good.
145 lots * $365 lot rent * 70 multiplier = $3.7MM
For the POH you'll need to see their condition and do a one time purchase of those based on what you can sell them for. So if these are worth 100K in aggregate then your total offer would be $3.8MM.
Also consider the lot rent and where it is compared to market rents - is it about right, overpriced, under priced, etc? If the lot rent is higher than most Parks in the area it may already reflect the inclusive utilities, and you need to consider that as part of the offer.
If the rents are below market or near bottom of the market you may need to have some flexibility going to a 75 multiplier as a larger park like this will likely pull a premium on the open market, but you need to feel out the Seller a bit to see what you think is an appropriate starting point.