Hello Julia, I am living in Porto for year.
What I see most is tech jobs and tech companies, it is where you wanna win money to live, other positions I see people winning really low money.
However if he speak so many languages he can try to make money online being a teacher, for English, French or any other language he feels comfortable to teach. He will probably win more money than work for tourism.
Rent nowadays is not easy also, the city center has too many Tourist and now you need to be more and more far away.
I hope I helped you.