First time buyer

First post to this board. Ordered Steve and Corey’s books. I have a opportunity to purchase a older park with 55 lots and about an acre of land. The property is in Central US, in town with about 35K+ population.

The owner keeps a lot of the info in a notebook. As for the property, I would be surprised if there is a home newer than a 1980. The roads are awful. The electric and gas are metered and the water and sewer are city although it is paid by the owner. The park supposedly has 40 lots rented and 15 empty, yet to be verified. With the calculations I have found on this site, can someone verify my numbers. Value based on lots renting for 140. Rented lots=336,000, vacant lots= 63000, for a total value of 400,000. I know there are a lot of variables, but am I in the right ball park?

Thanks for any response in advance.