I have no idea where you are fritz, but around here used stick welders are easy and often extremely cheap to buy used. I've bought them as cheap as $20 for a 220v AC only unit. The most I've paid for one is around $125, and that one is an industrial AC/DC machine that will put out over 300 amps. I also just bought a set of torch cylinders for $50...and they are the large ones. The oxygen cylinder is either a T or K size and the acetylene cylinder is a #4. I have seen complete sets with torch and cylinders sell for $300 or less. Often it will be the small plumbers size sets, but I have seen sets with large cylinders just as frequently for the same price.
There are two things to look for when buying cylinders from an individual. One is any ownership data on the cylinder itself. The second is the hydrotest date. This is a better explanation and illustration than I can offer.
https://youtu.be/ndGB-Ww47M4 Another thing to keep in mind is that if you aren't going to weld with a torch, you
do not need acetylene. Propane works just as well for cutting, and an acetylene regulator will screw right onto the propane tank you use for a propane grill(although there are specific regulators for use with propane). You will have to purchase different cutting tips for the torch itself. They're easy to find and no more expensive than a standard acetylene cutting tip. The last part of this equation is hoses. There are two grades, "R" and "T". Grade R is only for acetylene, while Grade T is for use with all fuel gases. Grade R will break down internally when exposed to the chemicals in propane or other alternative fuel gases. Lots of people use it anyway, but it isn't safe or recommended. Hose is cheap, so if you're buying it anyway, get Grade T.
Next is being aware of the withdraw rate limitations of your fuel cylinder size. This is especially important with acetylene since the gas is dissolved in acetone inside the cylinder. If you exceed the safe draw rate for the cylinder, you will end up pulling liquid acetone out of the cylinder and into the regulator/hose/torch. Best case, you wreck the regulator. Worst case, boom. There is a similar withdraw limit if you're using an alternative fuel gas like propane.
http://airgassgcatalog.com/catalog/E176_TAG_149.pdf Torches and regulators can be rebuilt if the diaphragms or valves are worn/ruptured. This applies to better known brands and not the chinese clone products though. It is far cheaper to rebuild a quality older regulator or torch than to buy new. I've had several rebuilt and it's usually around $40 to rebuild a regulator, roughly double that for a torch. Many of the regulators I have are no longer in production, but were $200-$600 new. I recently had a Victor 315 handle and 2460 cutting attachment rebuilt for around $80. It would have cost $200 to buy just the 315 handle.
I don't know what sort of welding projects you have in mind either. IMO, if you plan to weld anything thicker than 3/16", the 110v MIG/FCAW units are a waste of money and time, and even then many are insufficient. They might fuse two pieces of metal together, but the majority don't have enough output power for proper penetration into the base metal. In layman's terms, the base metal isn't melted into as much as it should be, so the welded joint doesn't have the strength it should. I'm not really a fan of wire feed welding anyway. It's far too easy to set one up in such a manner that the finished weld bead has the correct appearance, but lacks adequate fusion to the base metal. Failures of joints welded with this defect are commonly seen in commercially produced products. I have done it myself a few times. I'd guess that just about anyone who has ever welded with a MIG has done it a time or two.
https://www.millerwelds.com/resources/article-library/the-most-common-mig-weld-defects-on-aluminum-and-steel-and-how-to-avoid-them I would recommend purchasing a machine capable of 200 amps output. That puts you into an input power requirement of 220v, but it will be capable of welding pretty much anything you're going to do as a homeowner.
Different shield gases, or gas mixes, may be required depending on what you're welding. Most MIG welding on steel is done with either straight CO2, or a 75/25(Argon/CO2) mix. The arc will behave differently, and penetration will be more or less, depending on the gas/gas mix. I use 75/25 mix exclusively at work, though another choice would often be better. If you have a machine with limited output, choosing a different shield gas mix can extend it's capability slightly.
https://gowelding.org/welding/mig-gmaw/gasses/TIG: Not what I would suggest for the average guy to start with. It's not an easy process to learn and requires significantly more coordination. Also the most costly if you want a full featured machine capable of welding anything, and the slowest method. For welding aluminum, AC output is preferred and continuous high frequency output is required to use AC current when TIG welding. DC output can be used, but has limitations. There are several arc initiation methods, scratch start(just like striking a match), lift arc, and high frequency, to name three. Scratch start is the cheapest, and can be done using a DC output stick welder with an add on TIG torch. The torch will have a manual gas valve, and there is very little arc control available to the user with this method. It works, and is how I learned to TIG. Lift arc is
not a method I use. It is basically scratch start with the addition of a foot pedal(or other means) of amperage control. The tungsten electrode is touched to the workpiece, the foot pedal depressed, and the arc establishes as the tungsten is lifted away slightly. With high frequency start, you hold the tungsten close to the workpiece, then depress the foot pedal to establish an arc. Keep in mind that high frequency start on a machine does not necessarily mean it also has a continuous high frequency output option. The latter is typically a higher cost option on upper middle and high end consumer machines and pretty much standard on industrial machines.
I guess I should hit on duty cycle as well. Duty cycle is the amount of time in a ten minute period that a machine can be used, without overheating, at a stated power output level. Consumer grade machines typically have a 20% duty cycle at or near the maximum output of the machine, or two minutes out of ten can be spent welding with the other eight spent idle. The biggest downside to many of the consumer grade machines, especially the lesser output models, is that at any reasonable setting the duty cycle is still far less than what it needs to be for a large welding project. Commercial/industrial grade machines are 60%+ duty cycle at or near the maximum output. The average home shop guy is unlikely to ever approach hitting a duty cycle limitation with one of these machines. This is because at the output level you're most likely to use, the machine is capable of operating 100% of the time. As an example, that industrial stick machine I mentioned at the beginning has a 60% duty cycle at around 300 amps of output. Most stick welding is going to be done anywhere between 70 and 150 amps, so when welding with settings in that range, the machine is capable of running 90-100% of the time without overheating. By comparison, the ubiquitous Lincoln AC225(sold at home depot and lowes) is only rated at a 20% duty cycle, and Lincoln doesn't give any further information.
If you have anything specific, feel free to ask. I'm a machinist, but I also weld(mig/tig/stick) in a professional capacity.
Edit: I forgot to mention that you can build your own stick/tig welder from an automotive alternator and an electric motor or gas engine.
