want to convert a vacant lot into a RV storage

[Lea Hong]

The following story may sound silly but I honestly don't know where I should ask for opinions.

My family owns a 2.5-acre vacant lot in San Gabriel Valley in California. However, due to their negligence and language barrier, the land has been vacant for years and they ended up getting thousands of dollars of fine and bunch of violations because the homeless literally built a house on the land. Now they want me to help them with it because I live in the United State.

Since I live on the east coast, it is hard for me to active manage the land, so I talked to property managers and some agents. One person comes up with the idea to turn this land into an RV storage. noted this vacant land has no automated gate, no security camera, nothing. but he is willing to clean up the land and prepare it for the RV storage. after it's done, he will be marketing and managing everything. So I am basically like a landlord to his business. 

I know for a residential property manager, they usually only charge 10% of the rent for marketing and managing or a fixed number, but ofc the house is already ready to lease out. My case seems similar, except the agent will also be the one doing all the work beforehand, ofc the cost will be reimbursed. the question is he wants 25% of the gross income if his plan works, does this sound right?