As I described in the chapter dedicated to mortgages, while many estate agents will be happy to help you obtain a mortgage it is not advisable to rely on an estate agent to act as a broker. They will likely only deal with one (or a handful) of banks and generally work with the bank that gives them the most favourable conditions.
Now that the mortgage market is becoming more advanced and mortgage offerings are more varied, the role of a dedicated mortgage broker has become increasingly valuable. A broker will normally seek preapproval of a mortgage, from several lenders free of charge, advising you as the the best offer to suit your needs.
Most will charge a fee on top of the bank's opening fee typically between €500 and 1% of the loan amount. Despite the cost, using a Broker has obvious advantages. Not only will pre approval help you with budgeting and negotiation but by having knowledge of all the various products on the market, a broker will be able to find the best option for you, potentially saving far more than their fee in the long term.
While brokers do not need any official qualification in Spain, they should be registered with the Bank of Spain.