How to Invoice Vendors

We need to invoice a few of our vendors.  Sounded easy but when I went to show someone how to do it the Vendor name did not show up.  I know the easy work around is to just set up a new customer, but that makes it hard because a few vendors might want to pay cash now but in 30 change their mind and ask us to take it against open bills. 

So I thought maybe I should enter them as a vendor credit, but then what if i get a check?  How do I apply the check from the vendor to the bill credit.