Mama is not justified in giving Walter the money, because Walter is so selfish that he cannot handle a large sum of money responsibly, also Walter doesn't realize how unrealistic his dream is, and lastly, Mama doesn't believe in what Walter wants to do with the money. There aren't enough reasons to justify Mama's supporting his idea. Walter's idea of a liquor store ends up almost destroying the family when he gives when he gives him, and Bennie's college money, to a business partner, trusting the man to close a deal. Instead the man runs off with the money and Walter is left horrorstruck and penniless as a result of ignorance.
Walter doesn't seem aware of his ignorance. He is selfish to the point that he pays attention to nothing but getting Mama to give him money to give him money when the check comes. His assumptions that nothing could be more than goal start to tear his family apart.
Walter expresses that he would risk everything for his investment without considering what he could be taking away from his family. This isn't an exaggeration; he really doesn't consider those things until it does go wrong.
Some may argue that Mama just wants her son to be happy and have opportunities. After all, Walter's own sister is going to college in hopes of attaining a somewhat far off goal. Why shouldn't Walter have a chance at a goal Bennie got to try all kinds of expensive hobbies: guitar lessons, horseback riding lessons, photography classes, etc... Walter only wants a chance to support his family and every parent deserves that chance. Walter does show some maturity in his dedication and relatively organized plan. Mama just wants to be a good, supportive mother and she is.
The previous points are fair,