Invisibility is going to be very popular with monsters who want to go out in the world.
As far as scrolls are concerned: Xeroxing them doesn't work. Carbon paper does, even on gray paper where the runes are barely visible for intellectual property reasons, and tracing a xeroxed copy also works fine; a simple spell takes about five minutes to make a stack of four. The spells are available in French and Spanish. There isn't a huge selection to start. But it's something.
They give Angela an after-school job tracing them according to demand so they have more time to discover additional runes and work out additional spells, and they put up fliers in the Avalon advertising a mail-order service.
Bella gets a car. It's a beat-up station wagon, but it works.
Bella has a small business, a vehicle, and a long-term career plan.
She sets about making arrangements to skip the eleventh grade, and Darren follows suit.
The two of them are adorably attached to each other. There is a lot of kissing. Savannah teases them a lot and Bella messes with her and Darren blushes.
By the time summer vacation starts, they have a stabilized price point, sufficient regular buyers, enough repertoire, and a nest egg of money that permit them to rent a small storefront and hire a teenage griffin to sell scrolls in the Avalon. They are on their way out (Savannah accompanying for kicks, Bella driving) to seal the deal and drop off a batch of inventory. Bright and early.
"Should collect our prospective employee and buy him lunch and see if we trust him with a great big stack of scrolls and their instruction manuals."
Nod. "Hopefully he's not going to cackle and then go running off with his new found power of invisibility to spy in the girl's showers or something."
"That, too. Sorry, I grew up with Savannah, take a wild guess at what she wanted to use invisibility for."
"What, really? Savannah, you are aware that as a lesbian you have the coveted trait of already sharing gym lockers with who you'd want to stare at. Being invisible would make you creepier but not particularly more effective."
She rolls her eyes and doesn't reply. She gives an annoyed sigh, and then looks out the window, obviously not feeling talkative.
"Okay. Twin veto rules apply, what the hell is up? I changed the subject, are you mad at us for something and just feeling - weird and passive aggressive today?"
"Okay, Savannah, seriously, I am not blind and stupid, something is wrong. Tell me what it is and I promise not to mope or get passive aggressive about you not telling me sooner."
"Auuugh," says Savannah. "Shush. Just - shush, stop talking, that is what's wrong, you keep talking and poking me and it's getting on my nerves!"
"The fact that I am talking is getting on your nerves? That - what, that never happens, what topics are upsetting you so I can avoid them and stop upsetting you? You told me to go back to talking about magic, you think that's the most boring thing ever."
"Because I don't want to talk right now," she says, a bit off guard.
"Please stop being cagey, Savannah I'm your brother I won't disown you or something if it's terrible - is someone dead, is that what's going on?"
"I'm not fucking scared of you disowning me! I'm pissed off because you are bugging me for no reason and now you are interrogating me!"
"Yes," says Darren, frustrated. "You are, but I'm allowed to be worried, which I am, because you are my twin and I have never in my life seen you act this way! Please. Please let me in, Savannah."
"Is it me, I can, like, pull over and wander off for ten minutes if you don't want to talk about it in front of me?"
"... Let's go with pulling over and wandering. Savannah did you suddenly just start hating our relationship? I thought you were supportive?"