Generally issues with leaf shutters are most noticeable at slow speeds, so BobD's suggestion of testing by ear is usually OK. If the Yashica 24 will work with 120 film, it's hard to go too far wrong for $45. As you say, it's a way to test whether you like the format. Definitely look for haze or separation, but don't be too concerned about small scratches or coating marks.
If you were ready to invest $200, I'd say save the $45 and get a good Yashicamat 124 or Rolleicord. But even then, for $200, you're unlikely to get one that's recently serviced.
But be realistic. You're talking about a camera that is probably 40 years old.