If it turns out to be a problem I suppose I can merge them.
"You can have two unique accounts funded by the same credit card. However, if these two accounts serve multiple ads simultaneously for the same or related keyword, website, and/or business, it is ensured that not more than one ad from the following accounts will appear at the same time on Google or the Google Network."
In essence, it's the ad content that is restricted, not how you pay for it.