Sperm banks do give you money for your sperm.
Most sperm banks pay you between $35.00 to $100.00 per specimen and some people who go to sperm banks may $1,000.00 to $1,500.00 per month from their sperm.
However not everyone is accepted as a sperm donor but most people are as long as you have not HIV or other health issues that could affect the sperm then you will almost always be accepted.
People who go to sperm banks pay the sperm bank for the sperm that you donate to them.
You have to have your information on file with the sperm bank to prove who you are and have to pass health checks etc.
But you can make money from your sperm although it's not something I would want to do myself unless I was really desperate.