You don't need an agent if you know where you are going to purchase, although I believe any charges are paid by the developers. what you do need is a good independent solicitor ASAP, My Abogado is based in Torrevieja and came highly recommended from a reliable source, I will send you his details. if you are purchasing off plan your deposit will be around E3,000 this you could pay by credit card ( warn your bank before you come to spain) ... If you use a spanish mortgage your legal costs are very much greater than home financing.
The Roda contracts are straight forward, but you must use a solicitor to obtain an NIE number. I hope that is of some use to you..
A brief tale of woe just to cheer you all up, A few months ago we were in our solicitors office, an Irish couple came in off the street in a bad way, they had been purchasing off plan from a reputable ? Northern Irish company and had paid the final instalment, only to find the property they had been viewing was nothing to do with them. . This was their first visit to a solicitor, he was a a small business man who did not trust solicitors..