I bought one for $40 too, and it seemed like a decent deal. You’ll definitely want to hook it up to a shop vac or dust collector. I’m thinking of covering the disc since I don’t really use it. But yeah, I keep 80-grit on the belt all the time, and it’s super handy. If you get it, also grab one of those rubber belt cleaners—they’re awesome!
I wouldn’t bother with it unless you’re making small items like knife handles. A random orbit sander or a new belt sander would be a much better buy for the same price.
I really dislike this type of belt sander. The rotating wheel can be dangerous, and it’s not great for larger pieces. Handheld belt sanders are much more useful, especially for leveling boards after gluing them together. You can get a new one for around $40, so I’d go for that instead.