This is most definitely a scam.
What they most likely will do next is offer you the position (which would be really weird since they haven't even met you in person!!), then offer you a ridiculously inflated salary and mail you your first paycheck before you even begin working for them.
He will ask you to please cash it for him since he is out of the U.S. temporarily and does not have access to his bank account (bogus), and to please deposit the monies into your banking account. Next he will ask you if you could please forward him part of the amount to an out of country address and that he will reimburse you when he comes to the country.
If you do what he says, you will be majorly screwed by him. How so? Because the bank will find out the check is a fake, they will demand their money back from you and by then you will already have collected it and sent part of it to him. So you will be on the hook to the bank for what you sent him plus any add'l fees the bank may incur.
In the meantime, Mr. Scam is nowhere to be found and is off scamming the next person.
Report this common scam to sittercity.com right away and they will remove him from the site ASAP.