Hello. My I give my two cents?
Building new vs buying an existing new and the third option buy an existing.
I have built residential tract homes, townhouses, apartments, and custom.
I am a carpenter skilled in frame, to finish, to customer walk through.
I built (literally) my own home, lived in it for a few years and sold it.
My recommendation is do not try to be your own contractor; there are a host of reasons, more to list than this space will allow.
Building new through a building contractor is an option if you are not in a hurry; you are a good planner down to the smallest detail and have realistic expectations relative to your budget. Once you have committed to a plan stick to it. If you begin to insert change orders, the budget will change as well as the schedule.
Buying a tract home will get you in your home quicker. You will have a little latitude for changes, changes in the form of upgrades. Structural changes are either not feasible or the costs are prohibitive. In many cases, the builder does not use premium materials, fixtures, paint, siding, flooring etc. The grade of materials are termed builder grade.
Last, do not overlook buying an existing home. There are existing homes that have had considerable upgrades and have been well cared for. For example, here in Florida a recent flyer advertised an inground swimming pool in the mid $20,000. That is without the frills. When you finally sign on the dotted line, the price will have increased by a few thousand dollars. On the other hand, if you buy an existing home with a pool you will not pay a $20,000 premium.
I have provided a little more of a bio on my tool review web site, https://realtoolwiz.com/