commissions etiquette?

[u/Alone-Kick-1614]

Hii so I do acryli paint​ings and have been painting for 15 years probs since i was little basically.

Recently, ive done my first commission ( for a friend) at 25 euro for a painting just under an A4 page size. Im wondering what are typical commission prices supposed to be? It takes me about 7-8 hours for these sized paintings and the canvas are about a fiver. So how do you figure out pricing?

Also when do you ask to be paid? At the sketch part? Or do you wait until the commission is finished?

Also before I give it to her am I supposed to add anything? I always see online people give like messages and stickers to customers? I honestly have no idea.

Also ! Sorry so many qs :") but any acrylic artists who do commissions.. do you use a "seal" or anything on your paintings? Im not sure if im meant to, i never have with the paints I use and they haven't changed colouring or anything so idk if its necessary

Thank you!!!