Are food trailers/vans profitable?

Not in Victoria they are not 

I doubt so it’s already a challenge doing business 

yes yes and yes

long hours, weekend work and you need to find a good location

They can be expensive to set up and fit out. Then you need to pay for food selling permits. On top of that you have to be sure that the food you want to sell is what people actually want. Do some research, look at who your target market might be, locations etc. The best ones can make good money but you have to be avvailable when people want you, not when you choose.

Extremely.  Especially because they can declare a smaller income and pay next to nothing.

Yes yes yes.............

IDK but that food grosses me out.

If you have a good product that you can produce inexpensively and quickly...food trucks are indeed profitable.

GenCon (largest gaming convention in the US) was serviced by a fleet of dozens of food trucks.

They are generally profitable, but just plain lots of work.