When I was making a career change, I made a list of the top 10 companies that I wanted to work for. I sent my resume and cover letter to each of them. I ended up landing the job with my first choice. As it turns out, the person I replaced had just been promoted on the day my resume was received. The company's Human Resources Manager was passing my future boss in the hallway.
Timing is everything.
While you do want to inquire about a company's policy on telecommuting and flexible work arrangements, you should not let that be the focus of the interview. You want to leave the impression that you are a quality candidate, not that you are desperate to stay at home. Most companies don't offer telecommuting right off the bat. In most cases, you must work for a predetermined period of time before telecommuting becomes an option. Take a good hard look at your resume.