Hi there and welcome to the world of RVing.
To answer your question, many (most?) RV parks offer long-term rates for monthly stays or longer, as well as the more commonly cited daily and weekly rates. You may have to call to determine their pricing for longer stays but my experience is that most offer a monthly rate at a substantial reduction from the daily price. Monthly prices will often require that electricity used be paid for separately.
As an administrator for RVParkReveiws.com I don't know of any special method for determining which parks offer such discounts, but, since they're pretty common I would simply pick a few parks in the vicinity of where you wish to stay and make a few phone calls.
