When do you file the transfer of ownership?

This is probably a dumb question, but does the FAA track ownership by serial number before completion of a kit? Is the registered owner information of a kit available on the FAA web site just like any other aircraft?

I have been looking around at some of the projects for sale, and would like to get some advice on what to look for when looking at someone's project that is for sale. I have been to Aurora, and took the factory tour, and demo ride in a 9A, but find some of the projects interesting that is available ...