Earlier quoted context omitted.
It's not exactly out of "thin air", since we are trying to be nuanced here. If you take out a mortgage to buy a house the bank does loan you the money out of their own funds. It's just that the seller who receives your funds will put the money back into the banks (not necessarily the same bank, but the money market is there for the banks to settle among themselves). So in effect the sellers make the loans to buyers,…
> the bank does loan you the money out of their own funds Nope. This is the toy model of money and banking taught in high school. When a bank makes a loan, it creates money. The fact that there are stabilising deposits is a fortunate convenience. This is why leveraged finance is inherently unstable. The BoE had a good paper about this.
The bank must reach some level of capital requirement to make this loan. In other words, if the bank does not have enough reserves, they cannot make this loan.
The bank can use customer deposits as part of their reserves. They can also borrow from another bank (presumably, paying them interest). Lastly, i think central banks also have a reserve borrowing method (but not sure about this).