Any advice would be appreciated.
Although I've written songs going back to when I was a kid, I didn't really take off on doing it until I was in my 50's. Now I'm in a band that plays all original music, about 80% of which is songs I've written (and we make hardly any money at it) and I've written a ton of songs that people generally seem to like. I also perform solo at open mics and songwriter showcases. I say all that to say, the most important thing is to just do it.
A few more specifics:
1. If you're an investment advisor and CPA then you're a smart guy and, I assume, a reader. I found it very helpful and inspiring to read what other songwriters have to say. A few books that have helped me a lot:
a. Songwriters on Songwriting by Paul Zollo
b. More Songwriters on Songwriting by Paul Zollo
c. Saved By A Song by Mary Gauthier
d. How To Write One Song by Jeff Tweedy
*** There are tons more, and the genre of the songwriter doesn't really matter. You can learn useful things from a country songwriter
as much as a prog rock songwriter.
2. Find out where the songwriter open mics are in your towns (avoid the open mics where people just play cover songs). Go and observe and listen. It will inspire you and challenge you. Maybe you'll meet some folks to work with (as an example, the band Head & The Heart was started by three songwriters who kept running into each other at a particular open mic in Seattle).
3. Most songwriters will say (and it's true for me too) that sometimes a lyric comes first, sometimes a musical idea comes first, something they both come together. There are no rules. The most important thing is to be attentive to when an idea comes, and pursue it. Many songwriter keep notebooks with them to jot down ideas, or use their cell phones. Sometimes it take 30 minutes to write a complete song, sometimes it takes years
4. Get some recording software (Garageband, Logic Pro, etc.) or a digital recording device (such as a Zoom R24) and learn how to use it by making recordings of song ideas.
5. No, you don't need to know music theory (of course it's helpful if you do). By your age you've imbibed enough theory, such as diatonic harmony, by osmosis from listening to music. Even though you may not know the nomenclature, it will come out naturally. You already intuitively know what chords sound good together because you've been hearing it all your life. So yeah, grab a guitar (or bass) and start noodling.
Just my $0.02