Workout Suggestions?

Hello! So my boyfriend is a tow truck driver, and most of the time cooking dinner is out of the question because he gets home at ungodly hours. We eat really late, and we eat really bad. I want to start losing weight and eating better, so I've been eating: oatmeal or toast for breakfast with these breakfast essential shakes, and making salads or wraps for lunch, dinner is still hard.

I want to workout as well, but all the joints in my legs are really bad. I'm a waitress and a florist, so I'm on my feet most of my day and can't run or squat very much or it kills me.

Any ladies have some workout suggestions for those with bad joints? Modified workouts maybe? I'm thinking about getting a bike, but I'm not sure if that would be too rough.