When I retire, I would like to take up writing. Thoreau once wrote about a guy who intended to be an artist and kept putting it off until he'd made some money, paid for his house, etc. Eventually, the guy died before he painted a picture. He should have gone to the garret immediately. I think that you should write because you want to write, and worry about the rest later.
Agents usually look for people with established reputations, which makes it hard for the newcomer.
Your best bet is to write well and hope for the best. You could also look into various writers groups, such as Washington Independent WRiters or The Writers Center. One of my favorite books is Riddley Walker by Russell Hoban. I have three copies, two of which I lend to people, but no one seems to have the patience to read it. I'm also fond ot his other novels, including Kleinzeit and Turtle Diary.