That is, they shouldn't be paying interest on $50m sitting in their bank account right now, but would instead pay interest on what of the $50m they actually choose to use. I don't know if it's different in the US though.
I recall Richard Branson mentioning this sort of arrangement a lot in his autobiography as to how Virgin managed to keep going.
Debt itself (as a liability) is definitely not deducted from profit, but repayment of debt is deducted from the profit, and - what is more important - interest on debt is deducted from the tax base as a result. Which means that if you can load up on debt to get higher return, than you would get investing your own money.