To create a YouTube business account, you register for a standard YouTube account, because the company doesn't offer special accounts for business. It does offer special "brand channels" for business purposes, but companies register for those later, after they've signed up and created a standard YouTube channel.
So to create a YouTube business account, you go through the same process as an individual would who is doing a personal YouTube account signup. Either way, the use of YouTube requires a Google account, because Google owns YouTube and has linked the two for registration.
You have two choices: either fork over an existing Google ID or sign up for a new Google ID. Whichever you choose, the Google ID you sign in with will be linked to your new YouTube account.
Even though the forms for YouTube signup for business use are the same as for personal use, there are special considerations when you're registering a YouTube account for a business. These include deciding which Google account to link to your YouTube account and what kind of user name to select.
Don't Use a Personal Google Account for YouTube Business Channels
For a company using YouTube, it's not a good idea to use a personal Google account in the signup process. Rather, Google recommends that you use a non-personal email address in the YouTube signup so you'll be comfortable sharing those sign-in credentials with colleagues.
So let's start. Go to YouTube.com and click the "sign in" link at upper right. Then click the "New to YouTube? Create an account" link above the regular sign in box, which is for people already registered for YouTube/Google.