Custom Formula Field always giving an error

Custom Formula Field always giving an error

I am trying to make a formula field that gives me a formula based on the words in another field.  

If(Startswith(${Job Openings.Financial Quater 1},'F'),${Job Openings.Salary Position 1}*${Job Openings.Salary Percent},0)

No matter what return type I choose I get the error below.  I need it to search for a boolean, but return a string.  So what is the answer

Make sure you choose a Formula Return Type that matches the type of data your formula produces. (e.g. If your formula returns a string, then you should choose a Formula Return Type. string)