There are several synonyms for the phrase "money in the bank" that can be used to convey the idea of a sure thing or certainty. One such synonym is the expression "a sure bet," which can also refer to something that is a safe and reliable investment. Another possible synonym is the phrase "a guarantee," which likewise implies a certainty or a promise that something will happen as expected. Additionally, the term "a slam dunk" can be used to convey the idea of a sure thing or something that is almost guaranteed to succeed. Regardless of the synonym used, the central concept remains the same - a reliable and trustworthy investment that is certain to pay off.