And built an armored flight suit with weapons and propitiatory software powered by a device capable of generating enormous levels of electricity -while also being 1000th the size of a "science project" back home inside of a few weeks- using nothing but parts out of some missiles. Once back home he was able to recreate this suit with vastly miniaturized components AND a system to put it on him all, apparently, without anyone knowing. Guess Pepper never wondered why those contractors were coming in and out of his basement to dig the hole for the suit-donning device.
The only problem I have with the creating the "Stark-inium" in his basement is not that he could do it, Stark had proven himself resourceful. But that he created the powerful laser/accelerator in his basement powered by his home electrical supply. Sure wouldn't want his electrical bill.