BJJ value is a bit unique in that it’s a knowledge oriented trade. Since you’re not dealing with material goods, etiquette isn’t quite as clear.
You wouldn’t for example, walk out of a grocery store with a cart full of groceries without thinking of paying, or go through a checkout line asking the cashier if you can have free items.
Sooo…a few basic guidelines:
1) If a person has 1-2 more years experience on the mat than you, wait for them to ask you to train, as you’re the one gaining the bulk of the benefit.
2) An instructor is responsible for teaching during class hours. If they allow time for Q & A during class, cool, but if you want extra information, that’s what privates are for.
3) If you don’t have much money, showing up early and leaving late, as well as listening and drilling the crap out of everything the instructor teaches during class goes a long way.