Maybe that would be a good opportunity to offer them a quote for how much you could do the work for.

Yeah, that's what I do. Anytime anyone from a company sends an email about whatever, who wants me to help them (for their company) in private with something, I ask if they're willing to pay for my time spent on it, maybe 20% says yes. Most of the time they end up getting redirected to use the same venues the rest of the community has access to too.

Assuming you want to. But if you do, understand that accepting payment for services creates obligation to deliver, and possibly liability for poor performance. You may or may not want that.