Where do BBs get their funding for lending operations?

Sorry if this is not the right forum for this question, but it seems to be as appropriate as any other on the site. 

Bulge bracket banks are engaged in many different types of lending, for example warehouses/repo lending, revolvers to F500, etc. What are the typical funding sources for these loans? I would guess that BBs which also do consumer banking (becoming more common) use those deposits for cheap funding, but where else does funding come from, given that consumer deposits are probably pretty small at most of these banks and they are lending tons of money thru warehouses etc? When a BB calculates its NIM on a loan, where is the cost of funds coming from? Do BBs borrow against securities which are held in their PBs and actually belong to HFs? If so who are they borrowing from? 

Sorry if this is a dumb question or I'm not being clear enough, happy to try to clarify what I'm asking.