Repairing Arguments

Here's an example of an argument that needs to be repaired:

This book costs five dollars. If I buy this book, I will have no money left.

While the argument implies that I have five dollars on hand, to make this argument strong I need to explicitly say that I have five dollars. If I add that to the argument, then my argument becomes strong. I have five dollars on hand, so if I buy the book, which costs five dollars, I will have no money left. Even though it seems like a given argument that I have five dollars, It's important to add that I have five dollars on hand because it could turn out that the premise was all wrong and I only had four dollars and fifty cents on hand or something, and I just happen to be bad at math. It's best not to assume someone's implications are correct when you can have them explicitly tell you and verify for yourself whether the premises are correct or not.