If you do it right its no problem having an "outside" job, however when in or around aircraft it behoves one to have ones mind fully focused on the aircraft part of your life, not like so many who have their minds on their "other life" whilst flying. TSB reports have many reports with statements like "the pilot was president of the company which owned the aircraft" and other similar statements, I for one will not sit in an aircraft flown by such persons, and did in fact walk away from a few myself when the "very rich guy" wanted to play pilot, not all wealthy owners are like this but enough to make one very leery about such folks. {At our home field we have two such extreme examples, in fact bets are placed on how long before they leave smoking holes!} At the other end of the spectrum is the person with a very demanding non- flying job who simply doesnt have the funds or time to devote themselves to the degree required to stay current, doctors have a tendency to fall into this group. Having said all of this, yes, its possible to do both flying and other jobs, as long as one does it with care and dedication. Good luck to you!