I had hoped someone from your state might reply. I cannot speak for state specifics but perhaps I can point you in the right direction.
When you buy the park you are buying it subject to the existing leases. You would first want to read each lease and see what the length and terms are for each lease.
Then you would look for landlord tenant acts and manufactured housing laws regarding notice to vacate the property. Since these homes are more than just a leased TV, many states require 6 months or more notice that a lease is not going to be renewed. Non-payment of rent is usually the exception to this rule however.
I would also caution you against summarily evicting tenants based upon the age of the homes, at least in mass.
As homes come up for renewal or tenants fail to pay rent or perhaps they sell the homes, you might then require that the home be removed from the property. Just evicting a bunch of paying tenants because the homes are old is a quick way to cut your cash flow and you had better have a huge nest egg ready to blow on buying, moving, setting up, rehabbing and marketing before you see a dime (and only to find you are making a few more dollars each month after spending tens (if not hundreds) of thousands of your dollars.
Keep the bottom line in perspective. Be certain that this old park can accomodate modern sizes homes. Many times old homes have remained in parks simply because the land size, ordinance changes, set backs etc. no longer allow for another (or bigger) mobile home to be moved onto that lot.