If you changed your offer to something like, "Hey, I've got about $5k laying around, and I want to start a business, are you interested? What do you think we should do?", you'd probably see more action.
I personally think this has more to do with your friendship than the idea of your friends being mentally "poor".
If we were friends and I came to you and said "Look, I've got $50,000 I'm willing to invest if you can just come up with a new drug idea and start it," you would probably tell me you have no idea how to do pharmaceutical research. Well, most people have no idea how to start a business.
If I really wanted something, and someone offered me the opportunity to do it, yes, it may fail and I may lose that friendship, but if that stops me, it means I don't believe in myself enough! It may fail, but it may also succeed! Yes, failure in this case may also mean losing a friend, so the stakes are a little bit higher, but as a friend, he knows that I know he is likely to lose the money. So even if he fails, I will just smile and be happy that at least he tried.
But it's the same trap, you see? He does not want to do it, because he is afraid of failing, and losing money and the friendship. So he can say no, and give that as his excuse, but is that any different from any other excuse?
In this case, I could posit that the risk is even less because I am there to help him, if the money is gone he will not be in debt, he will just be back to where he started.
And you know what? Sooner or later, friends who don't stay at the same socio-economic level drift apart. Yes, there are exceptions, but in most cases people have friends in the same economic class. So people try to bring their friends up, like I try to do, and the friends who don't even want to try, will sooner or later lose that friendship that they don't want to risk.
It was kind of you to offer the money, but I wouldn't make negative assumptions about your friend for not accepting it. Consider the possibility that he has good reasons for not accepting it, and that those might be the correct reasons - that he may actually be better off without it in the end.
"If I really wanted something, and someone offered me the opportunity to do it, yes, it may fail and I may lose that friendship, but if that stops me, it means I don't believe in myself enough"
And what if you don't really want something, and someone offered you the opportunity to do it, and you didn't do it, would that mean you don't believe in yourself?
But it's the same trap, you see? He does not want to do it, because he is afraid of failing
That's why you think he doesn't want to do it, maybe. That's what you think your answer would be if you were in his shoes, maybe. Do you actually know why he doesn't want to do it? Have you asked? And listened to his reply?