What inexpensive tool is capable of locating neighbor WLANs if that is your only need?

A WLAN scanner (e.g., inSSIDer, WiFi Analyzer) is a simple, often free or low-cost tool that scans the air for available SSIDs and channels. It is used for basic visibility of neighbor WLANs, including SSID names, signal strengths, and channels in use.

From CWDP-305:

“WLAN scanners are useful for identifying neighboring WLANs, SSIDs, and basic RF characteristics. While not as detailed as professional survey tools, they are sufficient for quick checks.”

— Reference: CWDP-305 Official Study and Reference Guide, Chapter on ProtocolandSpectrum Analysis