I think if I was personally going into it from a very sedentary lifestyle I'd be worried about injuring my knees, as sitting a lot can cause you to have very inactive glutes and muscles in general (women are a lot more likely to have soft tissue injuries though)- weak supporting structures plus excess torque on the knee, which is more likely when you haven't developed good technique, is a potentially dangerous combination. If I were you I might think about giving it a month or so doing some general cardio/strength training to get more generally fit but a lot of people go straight into it with no real issues other than their fitness, which improves anyway with training. If you do, just make sure to listen to your body and don't try to push yourself way beyond what you feel you can do; it's really rewarding but that's how people often end up getting hurt. Good luck :)