i have a question about divorce

in what circumstances do they give. shared custody like whats the reasoning? or if the mother asks can she get full but the father can also see the children whenever he wants like no restrictions but the mother has full custody? also if it was shared doesnt the father have to pay child support and if not alimony? my husband (currently seperated anout a week) told me that he was talking to ppl at his job and he kinda was telling me that he wanted shared custody since i wanted to work and not take care of our kids ( he says cuz we r inbetween getting a divorce or just being seperated and waiting awhile before we do)if i chose to divorce him he says he would fight to get shared costudy because he says he wants to be in our kids lives and since i wanna work because obviously we wont be together and if i get full custody child support wont be enough for my three kids anyways he says that he wont have to pay child support? is he right would he not have to pay i dnt wanna have an ugly divorce but i feel like he is either saying stay with me or divorce me and ill fight for joint custody and not pay a dime?