A: The short answer is you can be an out of state purchaser but you need to right support team behind you. Signing the contract can be done electronically and you don’t need to be in California to do that. Either a real estate attorney or hiring your own agent.
A: A promissory note is based on when the loan is made, not necessarily when the note is signed. So if the siblings actually loaned the money, regardless of when the note is signed, then a backdated note is ok.
Review by an attorney is advised.