If you look around Spain you will see many Villas and apartments converted int businesses, on sector "A" for example Mercers used to trade from a villa and there used to be some villas off the top road opposite where the butchers are, that had been converted to commercial.
Also as Steve reiterated what I had said that it would be a very expensive process/
I am sure if you did get permission people may use it but you would have to be very competitive with your prices and you would not have the buying power of the larger companies.
Also, frequent flyer has said he had purchased a villa on a gated community elsewhere and has said there are many people selling up? although I am sure others will replace them.
Again best wishes but just get some advice from the town hall before you invest and possibly lose too much money,
ED