I came across this PDF

In the loan creation process, banks will make loans first (resulting in new deposits) and will find necessary reserves after the fact (either in the overnight market or via the Fed). Understanding the business of banking is rather simple. It’s best to think of banks as running a payments system that helps us all to transact within the economy. In addition to helping manage this payments system they issue money in the form of loans. Banks earn a profit in the means of transacting business when their assets are less expensive than their liabilities. In other words, banks need to source their ability to run this payments system smoothly, but will seek to do so in a manner that doesn’t reduce their profitability. Banks don’t use their deposits or reserves to create loans, however. Banks make loans and find reserves after the fact if needed. But since banking is a spread business (having assets that are less expensive than liabilities) the banks will always seek the cheapest source of funds for managing their payment system. That just so happens to generally be bank deposits. This gives the appearance that banks “fund” their loan book by obtaining deposits, but this is not necessarily the case. It is better to think of banking as a spread business where the bank simply acquires the cheapest liabilities to sustain its payment system and maximize profits.

To illustrate this point let’s briefly review the change in balance sheet composition between banks and households before and after a loan is made. Since banks are not constrained by their reserves the banks do not need to have X amount of reserves on hand to create new loans. But banks must have ample capital in order to be able to operate and meet regulatory requirements. Reserves make up one component of the bank balance sheet so it’s better to think of banks as being capital constrained and not reserve constrained. In this example banks begin with $120 in assets and liabilities comprised of currency, reserves, equity and deposits. Of this, households hold $80 in deposits which are assets for the households and liabilities for the banking system. That is, the bank owes you your deposit on demand. Our banking system has reserves already, but this is not necessary for the bank to issue a loan. It must simply remain solvent within its regulatory requirements. But if our households want to take out a new loan to purchase a new home for $50 the bank simply credits the household’s account. When the new loan is made household deposits increase to $130. Household loans increase by $50. Bank assets increase by $50 (the loan) and bank liabilities increase by $50 (the deposit). If the bank needs reserves to help settle payments or meet reserve requirements it can always borrow from another bank in the interbank market or if it must, it can borrow from the Federal Reserve Discount Window.