I didn't start flying until I was 27. Started flight instruction at 30. Cargo at 33. Made it to a regional at 34. If anything I think age might bring maturity and professionalism that the airlines will find desirable.
I advise anyone who is concerned about age to jump in. It is a fun job that beats real labor any day.
Downside: starting pay the first few years is liveable if you are debt free, live with your parents, and like cutting coupons. Otherwise have a back-up financial game plan.
I was 35 when I got my CFI, 37 when I started flying freight. Now I'm 39 and flying for a regional. Kinda like Keith said, you can't do it for the money, but if you love it, you can pay the bills and make a comfortable living after a few years.
Also, keep in mind that I started this whole process just before 9/11. It won't be nearly as difficult for you to get hired at your 'next' flying job because the industry is currently in an upswing. When the planes hit the WTC, I thought seriously about my decsion to go into aviation...for about 5 minutes. As much as my accountant thought I was nuts, I continued because I love it.
Every sunset I see from FL330 over Glacier National Park confirms that I did the right thing.
I was offered a job with Comair in the summer of 2001. I believe they went on strike and then the events of 9/11 transpired. Again I may have the dates wrong, anyway I turned the job down and am now Captain in a Citation 560XL. I changed careers at the age of 41, now I am 46. I took a $30,000 pay cut my first year leaving the electrical field and moving into aviation. It was not easy, but I survived the initial digress of wages. Good luck Hemispheres.