Note my response is NOT based on someone trying to build a wood framed house, rather it is based on someone who wants to build a massive concrete structure.
Permits and Permission. You need to understand very clearly where and what you are allowed to build. You can go bankrupt trying to develop the wrong land before a single bucket of dirt is ever moved. Neighbor lawsuits, land use restrictions, easements, building review, public notice, taxes, etc...
Of course this depends on where you want to build and if you are starting with a developed lot. An existing structure on a residential lot has crossed a lot of red tape, permits, reviews, and has underground and above ground utilities (if needed). Work with a real estate agent to find suitable lots, if you already have a lot time to visit your local building department. Get a property map, building code checklist, and a permit application paperwork. A local architect will be your next stop. Before you can go much further, you need a site plan and a survey to determine soil condition. You'll need a soil engineer to verify your site can support a massive concrete building without some exotic foundation so it won't sink (that much). Next you'll submit a draft permit to get approval and they will give you a ton more paper work or may reject it or require public review.
Finally you will need a hire a concrete building and engineering contractor. Post tension concrete and concrete buildings are a specialty. Everything needed to build a concrete structure requires experience and purpose built hardware which is seldom available to the public because it will fail if not installed correctly. Also a concrete contractor will give you your first real estimate of building costs and can identify the cost centers of your project. Never relay on an architects building estimate, they are not the ones doing the work.