Is this purchase worth it?

Someone is selling a desk stationary bike on FB Marketplace. I looked up the brand, Proform. My parents have a full-size proform elliptical at their house. They’ve had it for years. It’s been great. Not many reviews online. Although for $20, Im willing to consider ( if only the seller would reply more quick!) Despite the good deal I wonder if it’ll be effective. A goal of mine is just to be more active in general. So I could see myself reaching that goal while I do schoolwork online. I do live in an apartment on the top floor. The bike is able to fold up to be compact. I think it’s pretty neat. I know this post already sounds like I’m sold on the idea. It’s just maybe I’m looking for different opinions? The seller told me I could take a look at it before deciding to purchase.