This study analyses income determinants of freelancers (liberal professionals) from a microeconomic perspective. In contrast to recent publications a new database is chosen, the FFB-Online survey on Liberal Professions. So, for the first time information of professionals concerning their occupational experience, the single occupational groups, the start-up situation or to administrative professions' regulations. The theory behind the earnings function is human capital extended by institutional and start-up information. Beyond descriptive results - inclusive a new adjustement - we use an ordered probit model as the microeconometric approach. The results are compared also to multinomial logit results and a simple OLS estimation. In particular new results are given concerning the xtended human capital approach, occupational and instizutional effects for freelancers as well as impacts of the start-up circumstances.