What is real interest rate here and how is it different from inflation? I think you are trying to confuse the issue. I always thought the cost of capital (borrowing money) in real terms already included inflation. And then the nominal interest rate is equal to inflation plus profit margin for lenders.

Nevertheless, now let's proceed to the case where you don't borrow. 5% inflation and 5% deflation. You already have 1000$ and your profit margin is the same 2%. Will you be profitable under inflation in real terms, and will you suffer losses under deflation? You don't borrow, so you don't care about nominal interest rates (only about inflation).