Welcome to the forum!
I work 9-5 and currently in the last phase of my 24-week mountaineering training. Prior to this, I didn’t have much experience with a structured training program. 2019
training exercise volume was probably less than 200 hours. I started with avg. weekly volume of 3.5-4 hours and slowly built up volume over the last few months. Currently, I am able to manage around 10 hours of training/week and it jumps to 15+ hours if I do a long day trip over the weekend.
I do have some flexibility in my work schedule, so I can wrap up early on a weekday for a 1.5-hour steep hill hike locally. I live in Vancouver, BC so access to hilly terrain is easier.
Do you have an estimate of your average weekly volume from last year? That should help you get started with the new training plan.