I might just throw one little note in to this conversation, many people who feel they are sensitive to radio emissions are totally fine if you black out the LEDs which blink in the wi-fi router they are so scared of. So long as they can't see there is an operating radio device near them all their "symptoms" suddenly disappear, conclude from that what you will.
On a serious note: If you really need to measure a frequency, many voltmeters have a frequency counter mode built in, such meters are perhaps £30. This is for fairly low frequencies usually. And a Pi Pico £4 microcontroller can be programmed with an online project, searchable somewhere, to be a really cheap oscilloscope to look for higher frequencies and show FFT data. There is also a thing called an RTL-SDR for radio frequencies, about £20 for a "brand named" one where the manufacturer has verified it will work with GNUradio.