If you have never before been on H-1B status, nor had an H-1B visa stamp, then you can not start working until the new H-1B petition has been filed and approved. This H-1B status will require being counted against the H-1B quota, unless you will work for a cap-exempt employer. This also means that for most private and for-profit employers, the starting date for a new H-1B would be October 1 of the year.