To track guest payments which didn't reach property account yet, you can create a separate account (for example called Pending Downpayments) and assign to this account all payments you are awaiting but which do not arrive. 

Once payment is received you can transfer money to the proper account.

This way you will be able to see the account balances of each account correctly.

See also

Settings up Accounts

How to register a withdrawal, deposit or transfer transaction?

Transaction Date vs Accounting Date