According to JLT and Associates summary of their May 2006 Florida Region Manufactured Home Community rent surveys
Average adjusted rents (rents after deducting services) in the “55+” communities increased 6.9% from $310 to $332 per month. Most communities include some service(s) such as water, sewer, trash removal, lawn mowing and/or cable TV in the monthly rent.
You can find rent in the range your thinking about inland but probably not in the more popular beach locations. The cost of services and real-estate taxes have been exploding across Florida for the past several years.
Try Dogwood Acres in Ocala, Marion County, Central Florida's Most Affordable Seniors Community (352) 237-3283