humans do need money in life, but money is not everything, we should not exchange something very precious with money.
money can change a person. so be careful with your money. lest you forget things that are more important than money.
Income is not a basis of wealth, feel sorry for the girl but I know you can survive on it. Did you ask your sister to give at least good money for you to get a better life? because I believe blood is thicker than anything specially with money, but it looks like your greedy sister left you alone after everything you've done, karma will be on her side if ever.