Great advice to Dad & his son. You said it much better than I tried earlier. The difference in experience & perspective between an amateur (me) and a pro (you). Also recommended Musicians Institute for advice. Believe Nashville a good place to be, in addition to LA, NYC, or London. Perhaps not for more serious rock, but other contemporary forms...well beyond country now. He/they could find so many producers, artists/musicians, songwriters, coaches, music companies, performance venues. Also, I would encourage him/them to seek out members of The Players in Nashville or The Swampers in Muscle Shoals. They’re still at it doing recording sessions and producing young artists, and they’ve worked with a who’s who in music for decades.
Agree with the advice on locale. If you’re in a place where there’s not much going on musically because of the city/town size it makes it more difficult.