Architect
We also hired Cox-Evans Architects, and sent them drafts that Dawn and I worked up in a home architect program. The only thing we're really doing is adding bathrooms, and originally we weren't going to hire an architect at all, but the contractor wanted detailed plans before putting together an estimate. It's not a bad investment, however; since we have no idea what we're doing, having a professional (especially one sympathetic to historic renovations) review it is a Good Idea.
We read through some bathroom books and they basically said to add bathrooms, you needed to move walls and closets around to "steal" space. Well, Speedwell Forge was built before they had closets, and we're not moving any walls, so we had to "carve" space out of the bedroom. This is terrible from a preservation standpoint, but necessary from a business standpoint. (Shared baths just don't work in the U.S.)
Addendum: Bruce Evans, the architect threw out our plans and started from scratch. At first we were annoyed, but then we realized why he threw out our plans, and we're glad we hired him.