Creating a booking based on a POST request
If you are going to use a prepared statement (please do) then go the extra step of using placeholders and bound parameters. Your queries are not currently stable/secure.
If you don't truly need Property_No for anything, just return COUNT from your first query, and evaluate that value as a boolean (loose truthy comparison).  This is cleaner and more deliberate, I reckon.
Your code is suffering from excessive tabbing (aka "arrowhead" code). This increases the likelihood that you or future devs will need to tediously scroll horizontally to review/manage the code.
If all of the conditions must be true to reach the INSERT query, then just use one condition statement with the expressions separated by &amp;&amp;.