I try not to involve myself at all with plumbing. I'd say "I don't do plumbing" but lets face it I still have to interact with it some. My friends have to many stories about DIY plumbing projects that turning into DIY drywall replacement projects. I'm not a big DIY guy to begin with the plumbing just fills me with stress!
TBH, I've done a lot of plumbing but only minor stuff. I bought a pressure reducing valve almost 2 years ago with the intention of installing it myself but didn't get around to it. The $700 I handed to a plumber a few weeks ago was the first time in my life I've paid a plumber, if you don't count the time ~10 years ago I needed a trenchless sewer job that escalated into a coinciding water main replacement (they broke mine but told me that was unavoidable). It was paid for with an interest free loan from my town, not out of my pocket... yet.
The plumbing stuff I've done on my own includes 2 bathroom sink replacements (including buying and installing new faucets) here, trap replacements, washers in faucets (dozens of times), insulating the hot water pipes in the house's crawl space with foam, kitchen faucet replacement, toilet repairs of various kinds, valve replacements. I installed a washing machine, too, a supplemental side-sink to the washer as well (picked that up at Home Depot). Most of that stuff isn't too hard.
I've never sweated copper water pipes, but have observed it being done and I'm pretty confident I could/can do it. When that guy fixed my kitchen sink faucet scene a few weeks ago I had him install the pressure reducing valve... I'd intended to do that myself but had had ZERO copper pipe sweating experience and figured I shouldn't get my feet wet with that job. Besides, I have the money now, so I just said, fuck it, have him do it before he leaves. Funny thing is when the trenchless sewer job was done ~10 years ago and they replaced my water main they offered to include installing a pressure reducing valve for an extra $100 (including the valve) and I said no. I had no idea if it was a good idea or not. I should have said YESSSSSSSS! It cost me around $440!
Edit: My house could use a total repiping and the guy who fixed my kitchen sink a few weeks ago quoted me $7000 to do it. I'd do it now but for the fact that the walls would need to be fixed and I figure that's a big big deal. This house is 111 years old, they didn't do wallboard back then. There's a lot of lath and plaster, practically all, I guess. I might have it done anyway, maybe I can do some of the wall fixing. Once I get into a project I have a lot of capability. I have a lot of tools! There's a tool lending library (free) a couple blocks from me too!
I'm still not done with the kitchen sink, though. Even before the faucet fiasco I was into the project of fixing the sink surround, I have 1/2 the tiles removed all this time. I want to do that job before most anything else.
A guy here in Home and Garden had an idea how I could fix my kitchen sink problem I had this spring with parts I could buy at Home Depot and install with the use of oxy-acetylene torch, he linked me to a set at Amazon. I was strongly considering doing that, although I wasn't confident it would work or that I would do the work well enough. Having no experience welding beyond propane and Mapp gas, I decided to get an actual plumber. Two of my friends had leaned on me to call a plumber, one is a just retired plumber, the other has owned two houses and done most of his own work. He was really ragging on me. I finally gave in and went to Yelp. A day later, the job was done, but I had a big charge on my credit card.