Hi there - there are quite a few towns and estepona centre would be worth a look as in the old part there are quaint townhouses some still needing refurbishing and you may find a deal.
Fuengirola the same, Benalmadena Pueblo, Arroyo, Malaga itself although many are listed buildings, coin, alhaurin el grande as well.
Really you need to drive around and ask the locals as anything with agents would probably be a bit on the pricey side! If you speak some spanish you could go and ask local bar owners or shopkeepers as well.
Good luck - oh and I remember seeing a programme on Granada where people were doing the same thing!!