I'll bet my life the "different area" was Aragon......
If you ask the right questions to the right people,ie the local architects etc and stick to the rules,like in the UK you shouldn't have a problem.You can't build an extention in the UK without planning and if you do you will be required,at worst,to pull it down.The same,at worst, applies in Spain.
Use a respected and recommended estate agent and if ness.double check them with the users of this forum,most of us have been there and done that...Do lots of research and homework,there are loads of postings on this site related to building and renovating.