Finding the owner of a vacant house

[Nicole (Dunlap) Pendergrass]

Hi BP!

I just bought a 3 family house, which only shares a wall with a vacant two family house (which from what I hear has been vacant for years).  I'd LOVE to be able to acquire that one as well so I can have 5 connected units, but the owner is very hard to find.  I have a partner who has access to a people-finding program but that is not turning up any viable results.  He's also sent some letters with no response (their mailing address is still the property address).  I believe the house is in some stage of foreclosure, although I'm not sure how far along, plus I figured if anyone here markets to foreclosures/vacants you may have a good way of finding owners!

Does anyone know of a resource or person that is REALLY good at finding people?  I'm willing to partner up if we can actually get in contact with the owners and negotiate something.

Thanks!