I think that you will find that they dont rank very high generally. They may well be nice people but I think it is the occupation that hurts their reputation. How much percentage for showing someone around your home?
Our bloke, retired now, advised us on all manner of things and as a qualified ex-sparky was well know to help out folk with their electrical problems cheaper than most. Basically he was always around even if he's sold you a home. I guess you've got to look beyond the job sometimes and look at the person.