He would like to know how long the gap between the two jobs is.
--任何gap(指收到转的申请收件与离开老雇主的时间差)都是不合法的. 不过安全的gap最好少于45天.
After he get the new job, should the new employer file a new H1-B application for him or just transfer the H1-B visa?
--可以transfer,这样不需要新名额的控制,也不需要等十月一日.