Yes, "to be broke" is a correct structure in English. It is a commonly used phrase that means to have little or no money. It is often used informally to describe a financial situation where someone has run out of money or is experiencing a lack of funds. For example:
"I can't go out to dinner tonight; I'm broke."
"After paying my bills, I'm completely broke for the month."
"She's been struggling with her finances and is currently broke."
So, "to be broke" is a valid and widely understood expression to describe a state of financial hardship.