typically after I had parted with a few thousand dollars having signed up as well.
Rule no. 1. General rule everywhere not a reflection on the schools mentioned.
Never pay for flying up front. You are an unsecured creditor if the poo hits the fan. If they offer a discount for payment in advance be very wary. Many many threads on this forum on this very topic, many students losing life savings.
Some places may ask for a small booking deposit to protect them from tyre kickers, competitors stirring trouble and no-shows which is fair enough. Otherwise just pay as you go.
Good luck