Water leak

I have an underground leak somewhere in my front yard from a copper water main - 4 year old house! What is the going rate for leak detection? Any chance I can find the leak myself? The leak percolates underground ending up at the water meter box

lastly, who usually keeps the maps of the underground plumbing paths? the water utility company or the company that did the plumbing initially

thanks

Sometimes you can find the leak by following the water.
Most leaks occur at the meter.
With 4 YO copper, I would suspect a joint, not the copper itself.

Leak detections starts at $250 in some areas I believe, I don't have the electronics myself.

I don't know of anyone that keeps maps of water services.
Ditches can be straight to the house, or they can curve and bend, maybe someone left a pile of brick in the front yard that had to be avoided when the ditch was dug.