It is not hard to find CL banjo for under $100 but it will take a little work to make it into a comfortable player.

First you find one with a straight neck. One with an adjustable truss rod. One which seems stable, not all wiggly and loose.

Second, take off the strings and clean the neck. then buff the edges of the fret board to take out the sharp edges of the frets. A tiny file or abrasive board, like a fingernail buffer, can work.

Third, tighten up the head, put new strings on it, and adjust the string height by lowering the string slots at the nut and possibly the bridge.

Last, you stuff a rag (a damper) into the body so that it reduces the volume. Easier to learn if the jarring volume is not overwhelming.

A book on three-finger rolls is helpful. And banjo picks, naturally. Got tuning fork?

You could possibly find a local teacher and agree to buy eight lessons which include a loaner banjo. Most players have several, including beater banjos.