Asklemmy

Plumber or electrician.

If you're willing to deal with the later costs on your body, learn a trade.

Plumber, electrician, HVAC. Everyone needs something serviced, it's just getting your name out/getting with a good company. Bonus, these things can follow you anywhere. Big city to small townships.

Welding is another solid one. Good welders can be in high demand.

Again, be forewarned, take care of yourself now, and be ready for it to catch up with you down the line. It's rough on your body.

Utility locators.

Everytime someone digs a hole, whether to install a fence post or dig a basement, existing utilities have to be located so they don't get hit. Its needed literally everywhere rural or city, and very understaffed.

But its long hours and outdoors. Less taxing than other trades though, and women can do it as it doesn't require much physical strength.

I would say plumbing, electrical or general contractor. At least around me theres a lot of people looking for people to help with things like painting the inside of a house, caulking/grouting, general landscaping.

Sanitation engineer

You said you needed something more immediate, I'd say there's nothing wrong with being a waiter / waitress / bartender while learning something else. They're not the most secure jobs for sure, but they're not exactly going extinct.

Alternatively, hotel staff make a lot (at least a lot for the small town I grew up in).

If you're looking for a trade skill - HVAC, plumbing and being a mechanic will all be skills that will stick with you through life and they all pay pretty well.

Truck driving is really, really in-demand right now. If you're willing to drive 12-14 hours some days, shower at travel stops and sleep in your cab (at least, that's what I'm hearing a lot) then that could be for you.

Garbage men. You can shut down a city pretty well by not collecting any garbage. But I hope you're not in the USA. The way I hear it it's mostly really hard dangerous manual labour in that backwards country.

Doctors. Always needed even in remote isolated towns.

In a city with no prominent industry, people will always needs healthcare, childcare, food, and maintenance on their belongings.

Healthcare: doctor, nurse practitioner, nurse, dentist, dental hygienist. Skin and hair care might be stretching the category, but everyone needs haircuts.

Childcare: teacher, ECE, nanny. Big spectrum here from no training required to professionally registered.

Food: production, supply, distribution, and sales. So farmer (but that's capital intensive), food maker (baker, chef, cook, butcher) or distributor or seller.

Maintenance: vehicles (tires, oil changes, body shop, parts, detailing), homes (carpenter, painter, gas tech, electrician, window installer, roofer, landscaper), appliances (appliance technician), power equipment (mechanic, blade sharpening).

Probably more, but that should be a pretty decent list to start with, and all should be pretty portable no matter where you go, save for certain licenses that may be specific to a state or province.

Starting during the Great Depression, my grandmother insisted that every one of her children become either a teacher or a nurse, because those were the only people who were never out of work during the Depression. Both can be hard jobs (in different ways), but if you're looking for something where you're constantly employable, that's where I'd start looking.

If you want a valuable job that no sane customer wants to abuse, dentistry is an option.

Basic human needs,

Food, water, shelter. Go into any of these and you should be good.

Long term needs would add healthcare, education.

Plumber and electricians are usually employable and paid well, so long the city has that setup. It really depends on the type of place you live though. Higher income city? Landscaper/groundskeeper or house cleaner are good options, people are willing to pay to not need to do normal house chores. Many farms nearby? Livestock vet or slaughter/butcher. Lots of tech? Software/electrical/mechanical engineer, city depending. Someone mentioned teacher but I'd say look at salary first. Location depending, many are not paid well and the job can require up to 70 hours/week, which can be less than minimum wage of the same location. They also mentioned nursing, which is pretty good, but may require long hours depending on where you work.

Nearly every single business either employs a full time CPA or uses a CPA firm to check their books.

Salespeople. I'm going to get downvoted for this, but there's always good sales jobs for the right person.

Just one word: plastics.

Do you know any CAD? Civil is desperate for CAD drafters and designers. Doubled my pay. I design Substations now.

Hand jobs and cheeseburgers

Does the city of $200K have advertisements for city jobs? Rather than trying to be universally employable, maybe cater to where you actually are/will be?

what is your goal? Are you planning on moving to a different city and employeer every year, or just want to settle down in aspecific place?

there are lots of jobs. However some places have specifit needs. Some jobs can be worked remote from anywhere. Some jobs depend on word of mouth so you can't move after getting the skills.

How about being a mason, I need one for brick work and they are hard to find. Home inspections is a good one too.

Home Inspector. Every home sale needs one, they cost 400-600 hundred. You are not liable for anything missed or that can go wrong in the future. Just need your ladder and flashlight

I don't know if he's making good money or anything but in my town of around 100k there is one guy who is a bit of a jack of all trades (and to me it seems he could be a master as well, but I wouldn't know). He does stuff like copying keys, leatherwork, sharpening knives and so on. This is the guy you go to if you need some more obscure thing done. Might be something for you if you like that sort of stuff.

Do you really need 200,000 customers? Why not target something that enough people need to support you?

Like if you can find something 100 people in that city need, you’re fine.

Generally, any trade will always have good job security and decent pay. Trucking, maintenance (welder, electrician, plumber, or mechanic (diesel or heavy equipment, auto is usually over staffed) and HVAC) and accounting seem to have been the most reliable trades to find work over the last 20 years or so. Construction is very boom and bust. Medicine and maintenance are VERY short staffed currently, especially in rural areas.

In 2008 I chose trucking. Initial training was 6 weeks and cost me $10,000 USD back in 2008 followed by 3 months over the road with a trainer. Hate the job, but the pay is decent-ish (I've generally made between $55K and $75K), it doesn't usually matter where you live and the few times I've found myself needing a new job I've been hired within 72 hours of applying for the position.

If you do go trucking, avoid any company with a Teamsters Union presence like the plague. Every Teamster I've met to date has been an complete and total self-important asshat and they seem to have a tendency to call strike just for the hell of it (Though they are payed well).

Any other union is probably fine.

Like my grandmother used to say, there will always be a need for teachers and medical professionals.

Not promising either are easy to attain or will pay well though, much less have good working conditions.

Good luck!

Clean farming, medical (complete, mental/physical, many choices).