What do they want it for? Running? Walking? If for running, I seriously doubt you will find anything worthwhile in the sub $200 range...and yes, if they want to run on it and it isn't suitable for it, it WILL become a coat rack. In my experience, poor quality exercise equipment ends up not used...it's a lesson I learned the hard way by purchasing some crap stuff in the early 90's. Good quality stuff is worth investing in. I own a commercial quality Stairmaster (the real deal) and it is used extensively 20+ years later. It was expensive, but WORTH it, because it has gotten 20 years of use and I've put zero money into it. I also own a hand me down treadmill (3+ years) and had to recently invest $250 in it to make it work properly again (needed a new walking/running belt). Used, that machine in current condition would be worth $350-400. It is a decent quality item that sold for about $900 new (8 years ago). They still sell them for about that....this is my machine in the new version....it's a decent product for that price.
https://www.smoothfitness.com/treadmills/SFTL99514
Anyway, if you are determined to spend no more than $200, I'd look for a reliable work horse treadmill that is designed more for walking than running. There, you might find something. I'd look for one with an auto incline feature. Taking a quick look at my local craigslist, this one popped up....I know you aren't in my area, but this is one I would personally consider buying in that range:
https://minneapolis.craigslist.org/ram/spo/5912705061.html
Now, I KNOW you aren't in my area....this was just to show you what type of thing I would look for.
The big things to look at are motor size (2.5 hp is bare minimum...probably 3 hp if it is to be used for running) and length of the belt. Mine is 60 inches and again, if you want to run, that's pretty much what you want. Less than that, and running gets tricky, depending on your stride. For walking, 50-54 might be ok.
HTH