If you're dealing with a rent/lease manufactured home park/community you would need to start with the manager and would need to be approved by them before purchasing the manufactured home regardless of your age.
Once approved you would probably be able to purchase the manufactured home and become the "LEGAL" owner and put your seniors on title as "REGISTERED" owner and you would be fine. I'm currently doing this on some manufactured homes that I own and have never had a problem.
If, however, you're dealing with the purchase of real estate be it factory or site built you would be dealing with an HOA and they all have varying rules and regs and CC&R's that are generally strictly enforced.
I remember a couple of times trying to purchase in a 55+ community before I was 55 and was turned down both times even though I told them I just wanted it for an investment and would only rent to qualified tenants. Still a no go.
I believe as long as the occupants meet the requirements it is ok. ie: buying a unit for your parents. They may have to be on the "lease" but the management co. has no business knowing who paid for it.
Anyone over 18 can own the property, they just cannot live in it until they reach the age of 55. If you are interested in learning more, please email Trish Palacios, DRE# 01155737 at: firstname.lastname@example.org or call me on my cell phone 951-323-9034.