Organizing an event, legal requirements

Hi Everyone,

We have an sprl (own business) and want to hold a summer concert/vernissage - with paid entrance (the first time we will do anything music-related, although it was in our original business plan).

Does anyone have experience with this? I am trying to find out rules and regulations with regards to permissions, number of guests, required security and emergency health services. French or Dutch text is fine, if you can point me in the right direction.

Many thanks!