The only caveat is that the proposed project has to be a solid investment opportunity that has the ability to generate the cash to pay back the loan and any interest.
Which nobody wants to pay for ! Read Willy Walsh's comments on paying for it (LHR's biggest customer) and find me a passenger that wants increases in fares to cover said loans and interest. Do'able if the investment is modest, but this is a huge cost needing significant repayments that somebody is going to have to foot.