"Change the way you look at things and the things you look at change." - Wayne Dyer
Perception and credibility can't be underestimated when starting off as an affiliate marketer. I believe having a corporate website that can be used when applying to affiliate networks (and directly to merchants) will make me credible to those reviewing my application. I understand not to make things more complicated than they already are; meaning that a one-page website will be good enough to introduce myself (or my corporation) to aff networks, merchants, business associates, girlfriend(s), etc 
My question is, what sort of corporate tag line should I use on the site. Some examples below:
All of those are fine. It really doesn't matter for when applying to affiliate networks, they couldn't care less what your business tag line is - but having a website does at least raise credibility a notch.
This kind of thing will matter more when you actually run the business and deal with real clients.
You can find some good inspiration at
www.crayon.co