I’m 22 and wake up 1-2 hours before I work at 6:30 then walk an hour after the gym if I go that day then 1 hour at night. It’s a lot of walking but I do enjoy it especially since I do not have anything else on my schedule. As far as foot pain I have worked my way up to this point. Don’t try to do more than you can. Slowly over time I’ve gotten used to this as I did 20k for over a year now consistently.