caravan on a holiday park-Investment potential?

[poj]

I am looking at the possibiltiy of buying a caravan at one of the better known holiday parks(i haven't decided on what site as yet)I know that there can be a lot of potential pitfalls.
Any body with any useful info such as:-Void periods,ground rent,how long can it be kept on a site before it would be deemed to be too old etc etc.
Thank you in advance.