I know someone who recently went through the exact same situation. You have 10 business days as per the lawer my friend consulted but if you  were Fired  from the JOB then your H1B is cancelled  or cannot be transferred . But incases of lay off you can request your company to keep the H1B for a little longer and not notify the INS.  This will buy you some time. Most employers will deny teh request as it is illigal to keep anyone in H1B without the payroll. Within the 10 days of the period that you don't get paid you can apply for H1B from a new job/ company for transfer. If the process if initiated within the 10 BUSINESS DAYS, Then you are Safe. Most of the Madisey company will work with you in this kind of situation so talk to them for the H1B transfer incase you were LAID OFF.