Looking to develop land for RV and Trailer Parking, what to know?

[Nami Do]

So I own ~5 acre of land, I am looking to develop the land for RV and Trailer Parking. Land is in South Houston not too far from major airport and there are a couple residential builds near by. There is one RV park not to far from me that is fully occupied.

I want to understand what is needed to stabilize the dirt lot for parking. My hopes is to rent out the lots for parking. What should I know when going through construction. I know I would need permits and fortunately Houston does not have zoning restriction.

My question is when working with contractors what should I know. I know I would need a Stormwater Detention. I got quotes from a couple contractor and they said I need 6"-8" of gravel for parking. Is that true? I cant find many resources. Also the quote that I got the material cost is ~2x what it should cost (I called a local supplier for gravel).

Financing is not a problem for me. I want to make sure I am not taken advantage of from the construction perspective. Would anyone happen to know a good contractor that does excavation and surface stabilization. 

Thank you!