I/m sure zoning is different in different places. And I agree completely you should check the zoning ordinances, even if the acreage is zoned agricultural.
I live in an area that's zoned agricultural. But in order to have 'farm' animals, you need a minimum of 4 acres. There is also a zoning ordinance that says a maximum of 2 RV on the property. And it also says the RV cannot be used for a permanent dwelling place, since the property is "single family dwelling" and a permanent RV would then make the property a "multiple family dwelling."
So check before jumping in. YOU will not get into trouble, but your "landlord" may and then she'd have the embarrassment to have to tell you to move.
By the way $75 - $100 sounds about right. But prices may vary state-to-state!