1. Spain is similar to California in climate and area. If California is one of the richest states of the USA, Spain could be one of the richest countries of the EU.
2. You can establish yourself in Spain selecting the taxes you want to pay. Your company can be based in any country of the Euro area, with different tax law, although your production facilities are in Spain.
3. A cheaper work factor. The level of unemployment has reduced the labor costs hugely. But the most important thing it is the level of education that this factor has. Spain has a great number of bachelors and engineers that other countries as Germany cannot provide.
4. Spanish People are accustomed to work hard. This is a genetic fact. Aristotle said that shepherd people were most appropriated to be used in a war because they are accustomed to live in hard conditions. Remember that Castile was dominating Europe and conquering America with an economy based on the breeding of sheep, trading with the Dutch textile artisans that were under the authority of the same Spanish king.
5. Spain is “finished” (from a sentence of an old Spanish minister of infrastructures). The level of public infrastructures (highways, airports, high speed trains, telecommunications, and so on) is over its economy level. You can use modern infrastructures as in any other advanced country at the best cost.
6. Spanish people appreciate foreigners (with money). They will be welcome always. If you do not think so: look at Marbella. There has been a feeling of certain inferiority, that makes Spanish people to think that foreign people has a lot of thing to provide them always. The reduction of the prices of the houses let that your foreign staff management can find a fine place to live without expending a lot of money.
7. Spanish governments are busy enough squeezing Spaniards in order to preserve a huge state apparatus now and they will not pay attention to foreign investors.
8. Historically, Spanish unions seem to be only interested in perceiving money directly from the state instead of getting better conditions for workers. This will assure low labor costs for a long time.
9. Political fights are an opportunity. Catalonia has never wanted to be independent; they have always wanted to command in Madrid. Current interests only are showing that, as usual, their politicians are not able to do it. This internal competence can be an excellent opportunity for foreign enterprises to find a good place to establish with better conditions.
10. The incompetence of any Spanish government would never be disturbing, as all Spanish governments must follow the European directives usually driven by the countries with the most competent governments, and you will be protected by the European Court of Justice.
Now, you only need to know which the best sectors to invest are. I will give you a clue: Spain has many important enterprises at the construction sector (strong competence). Perhaps, you should search for technology based opportunities. Spain has the engineers, the infrastructures and the markets, but it has not the money.