I checked the parks within a 15 minute radius. They are all fully occupied and none have amenities. Lot rents were $450, $520, $610, and $650, so this park is right in middle. I would also put it right in the middle in terms of location desirability and aesthetics.
Expenses do seem very low at 25% and I agree there is not much upside to income other than pushing rents 10-15%.
I'm going to request financials and see if I can get him to come down at least 10% on price. I like the deal at an 8-cap, but I think the NOI number he gave me is an absolute best-case scenario.
Thanks for all the replies. Very helpful.