There are agencias inmobiliarias in every neighbourhood. Although their main business is selling property, most agencies tend to have at least a few flats for rent. Their fee is typically the equivalent of one month’s rent. This is an expensive alternative, but worth it if time is limited.
Room finding services are more proactive and cost a bit less. They charge an upfront fee (typically €60-120) and then try to find an apartment that meets your requirements. Although this sounds like a smart choice, these services aren’t always as good as advertised. You might be sent first to overpriced or substandard apartments in an attempt to unload those hard-to-rent properties.
In order to avoid this, it is advisable to talk to others who have used the service and to ask the agent to see a list of properties that match your requirements before you hand over any cash. They may not show you everything, but the best services will at least try to address your concerns. In case you do get caught in the situation of being sent to unsuitable apartments, you will need to be persistent and not accept a flat simply because it is the first one the agent shows you.
One final note regarding paid services: both real estate agencies and room finding services might inflate the prices of apartments in order to extract a better commission from the property owner. Don’t be scared of trying to negotiate a better price. The worst that can happen is that they turn you down.