Does the wedding have to be paid in full before the walk down the isle?
More then likely your venue will have you pay your full balance before the day of your wedding.p, as well as, your florist & DJ since they are providing you with a service you will use on the spot.
Other vendors who may need to provide you with an edited service more than likely will ask for your balance after you’ve viewed their work such as photographers & videographers.
Always always read your contract with all vendors & ask questions. It also never hurts to negotiate with all your vendor to ensure you get exactly what you pay for and want for your special day!!