If you absolutely must have Rhino 5 and already own a license, get it directly from McNeel’s legacy download page. Otherwise, do not pay for a used license unless it’s deeply discounted (under $150).
Rhino 5 is a classic, stable NURBS modeler that served the industry well. Today, unless you are stuck with legacy files or hardware, skip Rhino 5 and download Rhino 8 Evaluation (free for 90 days, fully functional). Rhino 8 is faster, supports modern Windows, includes SubD, and runs on Apple Silicon Macs.