Is there a State Law stating the minimum age a person must be to open a checking account. If so, what is that age? If it is 18, can the account be opened in the legal guardians name with minor as signer?

18 is the age of majority in Michigan, as of 1972. Here is a link to that act.

My opinion only - this goes back to 'know your customer'. The risk is that the minor will write a check that is ultimately dishonored because minors can't enter into contracts, and the bank will lose. If you know the customer, though, that may be a mitigating factor in evaluating that risk. I can tell you that we've opened demand deposit accounts for minors in the past, with an adult as an additional signer. It's a question of what level of risk you're willing to accept.