Pretty much what has been already said.

I used to ride 26-27 miles one way 4 days a week. Eventually settling on a Mon-Thurs routine. I'd then take the bus home in the afternoons. That 5th consecutive day was the killer. I just didn't have the recovery time needed. I tried a few variations, but couldn't seem to get 5 in a row no matter how I spaced the "rest" day.

I would like to have taken the bus in to work & ride home, but the bus didn't run that early. The bus home was cheaper ($2.75 total cost) than my car and time spent was about equal at 90-120 minutes.

As far as lessons learned: A shower at work is a huge plus. I wouldn't bike commute that distance if there wasn't a shower available.

Commuting 5-10 miles each way should be doable for most anybody regardless of facilities for most of the time. 10-20 miles everyday adds up with out recovery time. For you: I'd start 1 way with a bus home once or twice a week until you figure out what & how often the commute works for you.

Also, your food bill will go up a lot more than your fuel bill will go down. How much is up to you. I used to hit the factory cafeteria pretty hard on ride days. But then again theres nothing stopping you from packing an extra PB&J to eat when you get to work.

Many people also (Monday) drive in, leave their car at the office, then ride home. Then on (Tuesday) ride in, then pick up their car and drive home. They do this for the back to back training days, but manage an amount of recovery that works for them...Something to consider.