Open Source i different for different people. At first it came out of universities and academics releasing software to create the first and current ecosystems. These people were paid. There are also people that work on open source in their spare time - they get paid to work, and release things because they can. There are people trying to prove their skills to get employed later. There are big companies sponsoring choice requirements for their own benefit. There are dirt-poor people with some mad skill-sets who should probably balls-up and ask for some money.

Whoever you are, it is best to explain up-front what you offer and what you need.