You could just try a couple of short visits under your own steam to different areas first. Unless you are right on the coast, it can get very cold in Winter and you’d have to pick a house designed for that. We opted for the Canaries because it never gets very cold at low level. Although the Med coast at mid day in Winter might record reasonable temperatures, it rapidly fall away towards evening, unlike the Canaries.
Two books I found useful were
“Living and Working in Spain” by David Hampshire by Survival Books (http://www.survivalbooks.net) ISBN 1-901130-62-2-52195
and “Retiring to Spain” by Cyril Holbrook – Age Concern ISBN 0-86242-385-6