I think there are at least two kinds of debt - non-junk debt and junk bond.
If the company itself is not going to generate sufficient cash to pay back the non-junk debt, you may not be able to borrow it from others.You have to give a probability to the buyers.For a rational lender, he should put some covenants in the contract to keep him ahead of the borrower in payment.Therefore, the LBO player won't be able to put money in pocket without paying off the debt.The junk bond part of the debt is a different story. Once the LBO player get the leverage point (after borrowing the non-junk debt), he can start issuing junk bonds and do something he wants.