my uncle has a couple of acres well suited for storage of boat/rv etc. and i was wondering what level of security do you expect at such a facility, and what do you pay?

Outside storage, in my area, is $1.00 a foot in length per month. The measure from the end of the motor to the coupler on the trailer. They are behind a 10' chain link fence with razor wire on the top. There is 24x7 access provided by a keypad and electric opening gate. The also provide no insurance and usually require you have your own. Some have staff during regular business hours and some hours on weekends for new clients and customer service.  Some of the better ones, that have sheds, also have security cameras around.

The price should be free if it is your uncle!

If it is a field, make sure you put dryer sheets all over the inside, in each compartment.  This will help keep the field mice from getting in and eating all of your wires.