Help with cash offer for off market purchase?

[April Hamm]

I stumbled across a house that's about to be listed and I'm going to tour today.  I'd be paying cash for it if I like it, but would like the option period so I can get it all checked out first.  If I decide to move forward, what kind of paperwork is needed for this and where do we start?  I do have a realtor but she's not available to chat between now and my showing today.  Does anyone know how to proceed with this?