Formalities regards opening a restaurant (Lagos)

Hi guys,
one of my frd looking for some advise on below two points:
a. What are the formalities and certificates needs to open a restaurant
b. What are the formalities and certificates need to get for a mobile restaurant which will be on wheels, like in a van.

Please let me know the details like taxes, certificates or whatever is needed to be done.

Thanks
Shekhar