They are and can be a useful tool. I have had a couple of patterdale terriers through the years and they have made me look pretty good. When a person has had an animal in the living quarters and they are not sure he left the dog always gave me the confidence to tell them the animal was not in the living quarters. I could set up a positive set from a crawl space and clear it with either the animal getting in the trap or pay the consequences. You need to make sure your client is ready for that. On leash he would indicate on den holes that had animals making less sets. Afew times I used him in attics mostly on leash so I could retrieve him. It always made the family of coons move. I quit doing it because the insulation and dust had the same effect on him as me and he refused to wear a mask. Having a good dog is expensive and if you enjoy working dogs it is a good tool but he's not priceless so you need to enjoy him or he's not worth it.
I have a couple mountain curs that I have just started working and I am hoping to do some coyote,pigs,bears,squirrels,coons,ground hogs,feral and bobcats and whatever else we come across. To have a good dog I am going to work hard and spend a lot of money walking and running in the woods,getting wet and cold,hanging out with friends, shooting, looking thru binoculars. I'll probably have to buy some equipment that I didn't realize. A garmin Alpha for starters. I hope the IRS doesn't think I would have done all of this if not for this business