I wouldn't employ a private investigator at first, but if I saw I really needed this kind of service, I would finally hire him (or her). I haven't had any real-life experiences with a private investigator, because, in my family, we're all honest to each other and never lie. If we ever do so, we tell the truth at the end.
I wouldn't like to do this job, mainly because I'm not very good at creating deductions when it comes to clueless cases; the evidences would have to be very evident for me to solve a case. I never had a job, but I would like to become a teacher, a translator or a musician, concretely a pianist.