He's young and making mistakes, but if he operates on a long time horizon I think he's doing pretty good. He realizes the he needs to research a market before creating a product (customers own the problem, you own the solution).
His mistake here is that he's angry about YC (which is unjustified, they were right to deny him) so he wants to make an "incubator". That's probably not a good idea, but he's only 20 so has plenty of time to fail more.
I think he knows what to do though. Research an idea first before building. So, the smart thing to do would be to find a vertical that intrigues him and start engaging with people in that industry trying to identify problems they may they need solving. B2B (specifically B2SmallB) is always easier than B2C for a solo founder.