Good Afternoon Linda. Rents are usually fixed according to the park's fee schedule and length of tenancy. However it does not hurt to ask. I would encourage you to ask and see what terms are available. Good luck.
It's kinda like pulling hens teeth. MH parks tend to raise rents whence new tenants come about. The only way you could possibly negotiate a rent/lease is by taking advantage of the longest term lease they offer as a rule.