Finding an Address

I have a project where my client would like to find the nearest street address from where he current is.  Getting the longitude and latitude is easy enough but I'm having a hard time finding out how to get the nearest house.  I have found a lot of solutions for addresses maintained in a database but these addresses won't be in a database.  I thought about just querying Google for each longitude and latitude within in a small circle but my math skills are nowhere near good enough to accomplish that.  Anyone have any ideas?

Thanks!
Floyd