AFAIK they could buy you all of the ingredients and pay you to make them a whole batch, you are then providing a service not selling beer. It's probably toeing the line though.
I had a bottle that I must have forgotten to add carbonation drops to which I drank last night, still tasted good but the fizzy version is better. It was a dry Irish stout
I'm in the process of planning something like this https://www.homebrewtalk.com/diy-fermentation-chamber.html.
You can always scale this up or down to the sizs needed