Estimating an RV component within an MHP

Hi. How do I go about estimating the value of an RV component within an MHP. I know that with RVs you pay for utilities but how do you estimate occupancy? Right now the park I am looking at has 15 RV spaces and 8 are currently occupied. I can’t annualize that income. Any rules of thumb out there?

I own a park where the RV occupants pay the same utilities and lot fees the mobile homes do. Some RVs have been in here for years. So that may vary by park.