You'll also find the pawn shops full of clarinets (and saxophones) of various description. Virtually none of these will be playable without a substantial investment in repairs, and many will be so old that they have obsolete key systems.
If you intend to buy a clarinet, or other "band type" instrument, you'd be well advised to buy only from a band/orchestra instrument retailer known to have a good reputation with student and professional musicians in your area.
There are no bargains.
If you know an individual who has an instrument that they are currently playing regularly, and who perhaps is wanting to "move up" to something better, you might be okay; but even here it would be a good idea to have an independent evaluation of the instrument done by someone who plays the instrument and is without a direct interest in the transaction.
You can learn to compensate, somewhat, for small leaks and balky keys; but you don't want to contend with that while learning. An individual who's been playing the instrument he/she is getting rid of may not even realize how bad it is. And a decent new "student grade" will probably cost about the same as a somewhat better one that needs "a little repair work," - without the wait for the shop to get around to it.
Incidentally, for any one other than a "professional" musician, the "plastic" clarinets made by the few recognized manufacturers are excellent, and probably much less susceptible to "knockabout" damage you might see in "session" use than more expensive models. Unless you get into very stratospheric price ranges, they are vastly superior to any of the metal ones you might find. (Yes, they do still make metal ones - but you're not likely to find decent ones on the used market.)
As an off-the-wall suggestion - have you considered oboe?