Hi Roy,

What do you mean by valid address? If you mean does the address conform with USPS syntax and your user's computer is connected to the interenet, I would sugguest you write a little application that that goes out to the USPS website on the internet and returns their Zip+4 addresss.

Regarding who is the current owner, you'd need to buy data from a third party or connect to one of their websites to do that.

Good luck!

Hugh