Internship and Thesis

Where to work, in a company or on campus?
Usually if you find an internship or a thesis topic in school, you don't get paid, and if you do get paid, it is not a lot (around €400 a month). If you find an internship or a thesis topic in a small scale company, they might pay you a small amount of money, but they might not pay. THEN (drum roll...) if you get accepted by a large company to do an internship or write a thesis, they usually pay you. And what I heard is that they amount varies from €500 to €1000 monthly, and I heard the average is about €700 a month.

How long does it take for an internship or a thesis from start to finish usually?