to build a gun, like the author says, you don't necessarily save money, in fact i believe you spend more, cuz you want this part, or that part, over a "this will do part".
building anything can be satisfying that YOU did this, with YOUR own 2 hands, and what tools, and possible machinery you have, as the A-typical hobbyist. a professional machinist, of course will have more at home, or use of, at the company shop, in his off hours.
i will envy those that want to build a gun, or those that have built one.
i will do a "few" minor upgrades if i have to, or even want to.
but this old salt's thoughts are, i can go to the LGS, and get a gun, all built, in a box, most likely at, or maybe even just below the price one pays for parts, etc, to build one, and mind you, have it under a full warranty.
then, take it to the range and shoot it. then if it fails, say a few swear words, then call customer service.