The way it works is that if you create a mod, and there are some websites out there that can help you make some, such as Blender, the websites are free. I am sure they would take just about any major credit card or a check. Go to SCS.com and they have a contact page or may even have a place on there where you can ask about licensing on how much it would cost and what forms of payment they would accept. They even have an email address on the site for if you want to see about doing volunteer work for them. They are headquartered in the Czech Republic. SCS Software makes American Truck Simulator, Farming Simulator, Euro Truck Simulator, and they make Bus Driver. I am sure there are nearby colleges that might offer courses on how to mod a car, truck or school bus. And if you want to work for SCS, I am sure they wouldn't mind having some of us members onboard.
Seniors are just antique people rich with history.