Is a 22 inch road bike appropriate for a 5'9" person? I am admittedly a beginner and looking to purchase a used single speed bike just to casually use around the neighborhood. I came across this listing: 

https://nashville.craigslist.org/bik/d/murfreesboro-scattante-ssr-roadbike/6878047099.html

I am 5'9" (1.75 m) with a 30" (0.76 m) inseam. The seller claims he is also 5'9" and the 22 inch (56 cm) bike should work for me, but after some research I've been getting mixed answers. I spoke with a bike shop employee and he said this frame would be much too large for me, but there's a chance the seller didn't measure it properly. I was wondering if this size would work for me.
Unfortunately it is not possible to give you a definite answer.

A typical road frame of that size (56 cm) is usually too large for someone of your size (175 cm).

However, the bike may not be typical. Neither is there a typical rider. A bike that feels too stretched out for one rider may be just not cramped for another, assuming about the same height for both.

For a definite answer you either have to try the bike out. Or compare the geometry of the bike with a bike you already know.