How often should i do pushups and squats?

Hello. How often should I do pushups and squats? I'm a thin guy; I
don't intend to lose weight. I don't want to use equipment, I need
calisthenic exercises I can do anywhere. I want to do them to ward
against stiffness, and also to keep a toned body without getting
bulked up. Should I do them: twice a day, once a day, every other
day?

I also intend to the do bicycle crunches. How often should I do
these?

Thanks.