This assumes that there is very little or no profit in the business. Which in most cases is not true. I say the guy keeps all 50 and does without the third house on the beach.
In many business ventures, there is little or no profit. That's why so many fail, and take the investors' money with them. That risk of losing everything is balanced out by the possibility of making a profit.
But you may be right, and some business owners certainly are greedy. But in the overall scheme of things, very few businesses are wildly successful. Even if they are, who are we, or the government, to force that employer to spend the money where we (they) want him to?
What if I think you should pay me more to work on your computer, and that you don't really need that fourth or fifth rifle? Should I have the authority to force you to pay me more?
It all depends on your point of view.
How do we know he has a third house on the beach? How do we know he's not struggling with a second mortgage on one modest home? Most small business owners struggle - I don't know where you get this idea that they're all raking in the dough.
If "in most cases this is not true", then why have you not started your own business yet? (You see, I'm making the leap that you don't own your own business. If you did, you never would have made the above statement.)
So you want to force him to engage in charity. Why him and not you?