My advice here is to make a detailed list of what the various parts of the build will be (drawings, permits, foundation, framing, electrical, etc.) and decide what you would like to do yourself and what you will need to hire others to do. Get quotes on the work that you would like to hire out and estimate the materials you will need to do your portion. You may want to factor in your time into the cost as well, especially if you will be passing up other income to work on the project. At some lumberyards, you will be able to give detailed drawings to an estimator on staff who will do a material takeoff list for you of what you’ll need and what it will cost. When all the numbers come in, you can put together a budget and plan for an overrun allowance of around 15 percent. If you keep track of the materials and subcontract costs as you go, you can stay on track and make decisions as you go about the latter stages of the project without regretting it later. If it is challenging to obtain funding for a complete build, you may want to stage the build so that initially the frame goes up and the exterior is finished, and then you finish the interior work as you have time or as funds become available.
Let’s be clear about one thing: No workshop is perfect for everyone. If there were, I could simply give you a precise plan to follow with clear dimensions. Every person who comes to the hobby, avocation, or profession of woodworking has his own particular collection of tools and his own peculiar work style, skills, and desires for the kind of woodworking he wants to do that gives him a unique approach as to how he will lay out a shop: where the tools should go, where lumber and supplies are stored, and how much bench area he needs.