Most of the time you have to make the payment at the end of the business day for the property you bit to purchase.  

It seems like maybe ‘seller’s cold feet’ in this situation as you’re talking the very next business day the deal would close, which could be inconvenient no doubt, but not unreasonable.

But unless things have changed mightily from when I was last in a similar situation, I don't picture S8 being able to do it as fast as you closing today and getting a direct deposit from them on Monday (first business day after the 1st). 

I’ve had one close in about 25 days (not business days).

If they call the emergency line and it's not an emergency, I don't respond until the following business day.

The buyer never made the deposit within 1 business day and wants to back out now.

I also learned the reason we couldn't close the same is because in California the County clerk has to stamp the transfer of ownership which usually happens the following business day. 

@Jim Ziccarelli we have closed DSCR loans in as little as 10 days (borrowers that paid a rush fee for the appraisal) we can turn them in 3 business days.

The most common is an inspection period which allows you some time (I’ll generally do 10 business days) to do your due diligence.

This meant that instead of a few hours for a response at most, owners and tenants were having to wait up to 1 business day.