law on static caravans

could anybody please help us we have just returned from benidorm where we researched buying a static caravan or chalet to retire to and we got conflicting replies.two sites we visited said it was against spanish law for that area of spain to sell statics or chalets even though both had these for sale but they said it would be a private sale between the vender and us ,but after other stories we have heard about spanish law we are very sceptical another site we visited  which was british owned he said he new nothing about the law.