Back in the day (like 2005-2017), Google Adwords made it pretty hard and confusing to create accounts that allowed agencies or companies to manage multiple Google Adwords Accounts under one “umbrella” or “Master Client Center Account.”
In fact, it was so hard to do so, that Google seemingly dumped anyone with a Gmail or Google For Business (now GSuite) account directly into a regular Google Adwords Account when they signed up for Adwords.
This then prevented them from becoming Master Client Center Accounts.
If you’re confused on what I’m talking about, picture logging into a Google Ads Account and only being able to manage your own account.
A Master Client Center Account, now called Google Ads Manager Accounts, allows you to manage multiple Google Ads Accounts, meaning you can have multiple payment methods on file, and collaborate with other people managing the same account.
With the current version of Google Adwords, called Google Ads, not only do you not get stuck in a regular Google Ads account when you sign up, but you can even retroactively make your account a manager account.
This video, and this link, explain how.