I've been doing yoga off and on for 35 years, with one class to start me off. You might want to try a class to start with, finding someone who is open to teaching you given your situation. There are lots of books and tapes/DVD's out there, too. I have a wonderful yoga mat from gaiam.com, but you could do it without one if that means you'd start today. I always start my routine with Salute to the Sun, and sometimes do that over and over for the whole routine. There are lots of websites that show you how to do it - one is http://www.geocities.com/Athens/Ithaca/9012/salute_to_the_sun.htm. Good Luck! You'll feel better once you start doing it every day, and it gets easier - and you'll loose weight - if you keep doing it.

I should have mentioned breathing in my response. There are lots of websites that can tell you how to do this, for ex. http://www.holistic-online.com/Yoga/hol_yoga_home.htm. The breath is as important as doing the postures. With your mouth closed and your tongue at the top of your mouth just behind your top teeth, breathe in through your stomach, then rib cage then chest. Breathe out the opposite way - from your chest, rib cage, then stomach. You might want to hold the breath and apply the anal, abdominal and neck locks (clenching those muscles), then let the breath out and apply the neck lock while the next breath collects. You can practice just breathing excercises before you start with the positions.

When I first started yoga I was worried about making a fool out of myself in a class, so I bought a tape. I did that for about a month before I ventured into a class where I realized, everyone is focused on their practice. They aren't even looking at anyone else. And there is every shape and size in the classes. You really have to give yoga a month or so (in class)as when you first start, things are awkward and you need to learn the poses correctly. Why don't you start walking for 20minutes or so a day and following it up with yoga session when you get home? Start small so it's achievable and go from there. Good luck!
p.s. yoga changed my life, it is so empowering.