Do pilots design and build their own aircraft?
A rare few design and build their own aircraft. Most purchase an aircraft in “kit” (anywhere from a crate of parts to a mostly assembled aircraft) form or purchase a new or used fully assembled aircraft. If your passion is building, you might want to buy one in kit form. If your passion is flying (not building), then you may prefer to pay a little extra for an assembled aircraft rather than invest several hundred hours building your own. In my estimate, your time is more valuable sacking groceries for a supermarket than building your own aircraft, except for the joy and increased understanding of your aircraft the process of building gives you.