I would consider it but it would have to be very repeatable and well defined and at that point, why haven’t I automated it? The posited Agency of One sounds pretty much like a beginning-stage SaaS while you’re doing things on pen and paper or a spreadsheet until you’ve figured out what you need to actually build.

Otherwise, that seems like a fast track ticket to burning out. Retainer model and selling bundles of hours is going to keep your client incentivised to not waste your time.