"Extra borrowing" refers to the act of borrowing additional money, obtaining a loan, or taking on debt over and above what one already has. Full definition
That would provide lower interest rates to start with, but also plenty of extra borrowing capacity that should let the homeowner switch to a reverse mortgage later on, if need be. (moneysense.ca)
On the sensible side of politics there is the same enthusiasm for tax cuts but an understanding that there's no more scope for extra borrowing. (conservativehome.blogs.com)
Instead of offering reassurance on the deficit, we were offering extra borrowing. (theguardian.com)