Unless your rental is in Prentis Park though, you have just as much  chance of renting to a non-SEC 8 tenant as SEC 8 in Portsmouth.  

anyone have knowledge on valuing an RV park with long term tenants?

Mobile home parks are a very popular topic right now. 

In a walk thru they can give you a ball park number at best . 

She can get a fair rate of return that is sure to blow away what parking it in a bank account would provide and you can likely get better terms than with a bank.We love using a lease option model when filling a home like this because we often don't need to do all the cosmetic repairs that a normal renter would come to expect. 

For national lenders, no DTI, 30 year fixed, 6.75-7.25% interest. 30 day seasoning. 

Unless she brings something to the table in terms of REI expertise like a background as an agent, property manager, rehabber, or has the ability to find discounted off market deals or is at least super sharp and really passionate about a starting a new career in REI or something, I don’t see any reason why RE would be a better option than speaking to Vanguard and parking it in a high yield dividend index fund, if it isn’t already in something similar.

We are hoping to purchase a mobile home park as our initial investment. 

Currently working to update/rehab this property on the inside; plus new HVAC, parking pad, appliances, etc

Basically you need investors who have a lot of cash parked in a money market and aren't sure what to do with it --- the stock market is volatile but they know their savings are losing value every month because of inflation.