> Obviously Bill did better with those tools than most people would, but would it have been possible if he started as an average kid with an average amount of money?

Yes. Remember Woz had no money and no computer and still wrote Apple Basic. He wrote it in a notebook and hand-assembled it. An 8 bit Basic can be written in about 2K bytes.

I designed and built a 6800 computer in 1978, and wrote the software for it all in asm (the result was a VT-100 terminal workalike). I did have an assembler available which certainly made me more productive, but it was still small enough to do by hand. There were only 40 instructions or so in the 6800, and after a while one inadvertently had them memorized. You could hand assemble them as fast as you could write. In those days I wrote code asm in pencil in a spiral notebook.

What made Gates & Allen special was not their families, but their ability to see the opportunity that everyone else missed. When the MITS computer was the front page on Popular Science magazine, Allen saw it and ran to Gates exclaiming that this was the opportunity they were looking for, and they needed to get to work on it immediately.