Gap between end date and start date for H-1B transfer

[howlongmore]

Hi,

I'm asking this for a friend. This is the situation ..

1. End date at Company A is November 15, high chance that Company A
will inform USCIS about the end of employment
2. Start date at Company B is December 1 (tentative)
- Company B is betting on approval coming before December 1. I am not
sure if they will let employment start with just a Receipt Notice.
3. H-1B transferred filed, and Receipt Notice received

Questions:
1. Is the time between November 15 and December 1 start date considered legal?
- I think if everything goes well and the transfer is approved, the status is
completely legal.
- But what if the transfer is denied? Is the status between November 15 and
December 1 still considered legal?

2. The transfer is between 2 companies in 2 different states. How do people who
move between states deal with such transfer? Don't people need time to pack
and physically move? What kind of gap can be accommodated?

3. What are some options available to ask Company B to put the person on payroll
but not be paid? (who would pay you until you start working)

Thanks for your help.