You’re never too old to be a freelancer because it’s totally up to you what you do with your time. I was 25 when I started web development and I’m making a good living with it now. Business will likely be slow in the beginning as you slowly gain a reputation (if you’re doing a good job for those clients you have).
At first you should build some skills by practicing a lot. Your first project should be to build yourself a portfolio site. Even if you don’t have anything to show yet, this will get you in the game with designing and coding etc. Learn from how others did their websites. If you have a clear idea in mind as to what you want then you’ll eventually get there. Also, a good way to practice and build your skills before you claim to be a professional and work on projects for serious money is to do some pro-bono work for local/community associations. This way you can also build some reputation to display on your portfolio for when you bid for serious projects.
If you feel confident enough to design and/or build sites from scratch then go to relevant job listing websites to find people that look for help and apply for projects. I’ve made good experiences with http://authenticjobs.com
. And don’t let yourself be demotivated if you are rejected, that just goes along with being a freelancer. The next bid could be yours again.
But besides all the designing and coding skills you should also gather some knowledge about legal things like how to write proper contracts and project specifications so that you don’t end up being shortchanged. But you’ll grow with the challenge and if you’re eager and disciplined you’ll eventually be successful.