orauball: I am looking at doing the same thing across the Strait, on the Island, and have done a ton of research. You will find an enormous amount of information on this forum. As well, the Hot Dog forum is very suited to mobile-type inquiries and tips.
localnet is right, you really have to start with your inspector. If you are going to be a fully-fledged restaurant unit, you will require the same standards as a bricks and mortar establishment, e.g. 4 sinks plus mop sink, commercial extraction fan, sufficient fresh and grey water holding, etc. All these requirements are on the BC Gov’s website and you can pick up paper copies and booklets from your local enviro-health unit. Mine were very helpful and they even have trailer floorplans. However, if you are serving pre-prepared food, you do not need as much equipment on your truck/trailer but you must have a certified kitchen (referred to as a commissary in the U.S.) for your initial cooking, storage, return clean-up, etc. This could be a rented restaurant kitchen (the trailer in Vancouver  called “Re-Up” uses a restaurant kitchen in Gastown, for example), a local community hall’s or a church’s kitchen that’s certified. We are probably going to build one in our home.
How big and what equipment you need will depend upon what food you are preparing. I haven’t fully decided on my items and it’s a bit of a “chicken and egg” situation when you haven’t; very difficult to proceed on kitchen/truck/trailer designs without firm decisions about the menu.
Either way, if you are thinking beyond hot-dogs, the cost of doing business will not be cheap and you will start well into 5 figures. Let me know how you get on.
 
Karen