When calculating your budget for buying Spanish property remember if you live outside the euro zone, your money will be subject to currency exchange rates. Exchange rates always fluctuate, sometimes by a lot over a short time.
If you will be using non-euro currency to finance all or part of your purchase, you can arrange to buy euros in advance (this involves the exchange bureau or bank agreeing to a fixed forward exchange rate for a specified time - the longer the time specified the less favourable the rate).
If you fail to do this and your home currency declines against the euro, your available budget will be lower. A significant fall in the value of your home currency during the period between contract signing and completion could cause you serious fincancial problems.
You could also opt to transfer all your money into euros before beginning your property search.
In essence, it is absolutely vital to know exactly how much you have to spend in the local currency.