RV Park - FMV of Property Management

[Chadwick Hill]

Hey all! I have 50/50 ownership with a relative RE agent who is managing the RV Park and we are trying to determine the FMV of her services. The RV park is 30 spaces, no amenities (pool, etc.) and most of the tenants are long term (all pay monthly and sign one year leases, although we do let them leave earlier if needed). I'm short, this isn't a daily or weekly RV park, but more long-term in nature.

What is a fair way to compensate the manager, more similar to a property management fee (8-10%) or rent, or something different? Any real world experience would be much appreciated!