The analysts lobbed in some questions to clarify assumptions on the conference call. Read the Q&A towards the end of the transcript. Unfortunately, several of the CEO's responses were "inaudible" (and the CFO may have also made some "inaudible" comments).
For what it's worth, the CFO mentioned that they were expecting synergies from the deal.
You raise a good point about the cost of capital. I believe that FLY's existing debt has a weighted average interest rate around 4% (taking into account the swaps). The debt assumed with the new portfolio will have a weighted average interest rate around 6%. Maybe FLY can refinance into lower-cost financing, but maybe not.
Final comment: they mentioned that the new portfolio should be accretive to unrestricted free cash flow. But I haven't tried crunching any numbers to pinpoint a number.