Spanish Working Permits:
If you are an EU resident you don't need a permit to work in Spain. However you do require a Residence Card, which is usually issued for 5 years.

A non-EU foreigner who works in Spain must have a Work Permit and a Residence Card. A Work Permit (permiso de trabajo) for a non-EU national is initially valid for one year. When this expires, a five-year permit may be issued, but it carries restrictions as to geography, work, employer or a specific industry. 

If you're an EU national you can enter Spain as a tourist and register with the Spanish national employment office (Instituto Nacional de Empleo/INEM) as a job-seeker (demandante de empleo). You have 90 days to find employment. As a visitor, you can obtain an extension after 90 days, or you can leave Spain and re-enter for a further 90 days. When you are offered a job, you should obtain an employment contract (contrato de trabajo), which is necessary when applying for your Residence Card.

A Work Permit can be obtained if you are self-employed and it is suggested that you seek advice and guidance from a Spanish attorney familiar with the Spanish labor laws, as there are several types of Work Permits.