I dont know details, but when you work on construction and you have some expirience, in towns like Poznan or Warszawa you can earn about 1000 EUR (3600 PLN) per mounth if you are hardworker you can get more. And in this occupation you can get this job without any problems.
Generally painters charge by the square meter. around 10-12zl per square meter for a prepared surface, and a lot more if the surface needs to be prepared (ie. smoothed, sanded etc.)