Hi @Fernando Cantini, nice to be reading your plans. In terms of where to invest there is only one answer: it depends. It depends where you know people you trust, people that deliver quality work, and people that can perhaps show you the rules on the ground. There are good opportunities to be created in every of these markets. We decided to run our projects in Barcelona and Valencia, the North-East if the country.
In terms of flipping multiple taxes per country apply. Don't forget that there are still nice gains to be made next to the taxes. In Spain it is 10% when buying an apartment, and 19% over the profit that you are making. In terms of loopholes, there are some. @Adrià Creixell is the one who can explain this best for Spain. Keep in mind though that you need to know exactly what you are doing going this way. Only more reason to find people who can give you the guidelines.
Are you new into real estate? How did your interest arise?
Erwin