Not the lowest, for sure, but I'm going to put my hat in for auto technicians. Master techs can make over $100K in southern New England but the cost of tools can easily rival college tuition by the time you're a master tech. Everything except proprietary equipment and the car lift needs to be bought by the technician, which can cost thousands of dollars. Health insurance is prohibitively expensive, the flat rate pay system means you only get paid when you complete jobs, and it's an ergonomic nightmare because you're picking up heavy objects and working in cramped areas all day.
As someone who whose fiance was a mechanic until last year, I think it's really disingenuous to hear so many people say that the trades are your fast track to making money. Very little of that $150/ hr that you pay goes to the person working on your car. For every lift the shop has they're taking 80% or more off the top of that $150/ hr, and if the job takes longer than expected the mechanic doesn't make any more money. In fact they're losing money because they're stuck figuring out a solution instead of moving on to the next car.
And don't even get me started on tool loans. It's straight up worse than student loans because they're classified as personal loans. My student loans all hover around 5% interest, but right now personal loans go up to 18% depending on the term. The only saving grace I can think of is that they're usually dischargeable in bankruptcy.
I really could go on all day about how broken it all is because I've lived it secondhand for a while now, and now that I'm trying to gain more of these skills for my classic motorcycle hobby it's all so obvious. Not sure if the other trades like plumbing and welding have the same "take out loans to pay for tools to make money to pay for the loans, then learn more skills within the trade to make more money, and then take out more loans for tools to do the more advanced work" cycle but no one ever mentions this when they talk about how this kind of work is so lucrative.
Don't get me wrong, college is really badly overpriced in the US, but the trades absolutely can be just as expensive once you've made it your career. And I don't want to dissuade people from considering it as a career, either, but it's a monetary risk that you need to really sit down and calculate before you take the plunge, just like college.
lol please go touch grass