I think it depends on how you present yourself in an interview. Airlines are looking to hire full time line pilots, not entrepreneurs interested in dabbling in airline flying. I know of a guy who was rejected by my airline because he gave the interview panel the impression that he placed a higher priority on his business ventures than being an employee. I think, and rightfully so, that many potential employers might consider a side business a distraction, especially during phases of your career such as initial training that require your undivided attention. As long as you leave them with the impression that working for the airline is priority one for you, having your own business should not be a problem.