You could do a lot worse than contacting The Easy Horsecare Rescue Center
http://www.easyhorsecare.net
Please bear in mind though that they are very busy so it might take a while to get a response.
We have had our own horse here in Spain so can give you some advice.
Stables,, If possible build two and get somebody with experiance to rent the other one which will give you a little bit of help towards the upkeep and invaluable experiance along the way. The stable should be at least 12ft x 12ft although if you have the space build it a bit bigger. If you then get a small pony at a later date to keep the horse company, they could share the same stable as long as they get on. Horses are herd animals so prefer company and do better with a friend. Remember they also like to be comfortable so ideally rubber matting is good and will save money in the long run as you wont need as much bedding. While wer'e on the subject of bedding, wood shavings or straw are both good. You can sometimes get wood shavings from the local wood yard, but do not use hardwood shaving as they sometimes contain arsenic which can be absorbed through the skin. Also when building the stable remember your horse is going to pee in there, and when they pee there is a lot of it, so a slight slope going towards the door is a good idea. Try to build the stable with the door away from the prevailing wind as well. If possible an overhang is also good to keep out the sun and stop driving rain getting in.
Feed. hay is ideally the best, but is hard to come by in Spain and can be expensive so you can substitue clean oat or barley straw, but never wheat straw as it can give then cholic which can be fatal. Mix the straw with alfalfa but remember that it is high protein so not too much. Be led by the person who had the horse before. There are good commercial feeds available like fastfibre or other brands, so if you can find these then all the better. Try to avoid the Spanish cereal based feeds as they are full of oats.
Water. make sure you give them clean fresh water every day and scrub the water buckets to avoid the dreaded cholic.
Find a good blacksmith, mosy horses out here only need shoes on their front feet or you may find your horse does not need shoes at all.
Make sure you worm your horse regularly and that it's passport is up to date.
Good quality and good fitting saddles are a must. The treeless saddles are pretty good and a lot of horses find then more comfortable.
The list goes on.
Shade in the paddock is also needed so that your horse can get out of the sun. Also access from the padock to the stable is a good idea. There are probably lots more things, and if you have any more questions just drop us a line via the forum
Chris and Mary