My gym is near to where i work so i go during my lunch breaks for half an hour everyday except Wednesday and the weekend. Wednesday is good to take off as a rest for your muscles to grow, otherwise you'll just continue to rip them and could cause damage. However this shouldn't be a problem if your not intending to lift too many weights. I would recommend maybe 15 mins warm up excercises with light dumbells and those big balls to stretch the muscles, then 10-15mins on the rowing machine or do some running or som cycling for some aerobic exercise for losing weight. Also swimming is good if the gym has this facility.