The first part works unless interest rates drop and the savings rate is no longer equal to the loan. Five years is long enough for anything to happen. But if you have a loan that lets you prepay without penalty, that’s okay. You could make a little interest until you can’t and then be done.

Buying stock with it is high risk. What if your investments tank? Can you still pay back the loan? That’s leveraged investing, which is highest risk. Unless you can afford to lose more than 100%, it’s a bad idea.