I am coming at this from the perspective of a designer. I agree that construction should not begin on anything before the design work is done. Understanding the budget, both client and contractor, is an important piece of the project. The client should be comfortable that the “ballpark” cost of the total project is in line with their budget so no one is wasting time on something that can never happen. Assuming they have an appropriate budget, design work should come next. The timber frame and house design should be done simultaneously in order to achieve the best outcome for the client. Forcing a house plan onto a frame or forcing a frame into a house plan will not get you the best results. I tell clients that a timber frame can be made to fit just about any plan, but it may be overly complicated and costly. Conversely, I can make a plan to fit a frame, but they may have to make compromises in the design in order for it to work with that timber frame. The best way is to integrate the 2 from the beginning of design. Making adjustments to meet expectations is a lot a lot easier and cheaper on paper than in the shop or on the construction site. The client should find a designer that is familiar with timber framing or a designer that can work with you to coordinate the timber frame with the overall house design. Once you have a solid design in place, a more accurate price can be put on the project so everyone is on the same page when construction begins. Hope this makes sense. Good luck.