buying property in kythera...

we have just returned from a holiday in kythera, and are interested in bying a house or land. we have seen a large block which seems really cheap compared to others.it sounds too good to be true if all the tell us is correct. it is 11.5 acres and they only want 50,000 euro. can any one advise us how we can check things out? i know we need clearance from the local forrestry, but what else? they are a great family,(the vendors) and well respected in their community, but how do we know all is ok? thank you.