Many trades and plumbing in particular have a large complement of contortionism. I do a small amount of home owner plumbing, but I wouldn't be likely to do it as a second career because pretzeling to get to the sink fasteners gives me aches for a week; and I'm not going to dig out underground pipes in easy soil, but around here it's all rocky stuff.

If I was apprenticing 20 years ago, the pretzel work would be fine, and I would probably be more willing to dig.