WordNet sense 1 (yielding a fair profit):

gainful

WordNet sense 2 (yielding material gain or profit):

profitable

WordNet sense 3 (involving gainful employment in something often done as a hobby):

nonrecreational

WordNet sense 4 (engaged in a profession or engaging in as a profession or means of livelihood):

professional

WordNet sense 5 (leaving no balance):

square

WordNet sense 6 (receiving or eligible for compensation):

salaried, compensated, stipendiary

WordNet sense 7 (for which money is paid):

compensable, remunerative, paying