You dont say where you are looking to buy and what. One thing you should look our f=o if purchasing inthe Valencia Region (and now I believe in Andalucia) is Land grab. It was meant to have changede but it is the same law in a different cover. Whatever you do whether buyingprivately or through an agent do not buy proeprty that is Suelo Rustico and please ensure you get a lawyer that is not in anyway associated with the client – best to go out of the area.
If the seller is Spanish then check to make sure the person selling it is the rightful owner – you may find there is a chain of owners because it has been handed down through the ages and no-one has bothered to register the changes. Therefore there coudl be comlications.
Also if you are buying an old property if possible get a survey done. Dont know what area yu are looking in but in the Valencia region I know of a couple of UK ARICS qualified surveyors (who are now members of the Valencia College of architects) who can do this for you. I am sure there are others. You may have a dream of doing up a place but it can easily turn into a nightmare because the work is ten times what you thugh.
Other than that it should be fairly plain sailing.