Contacting owners of houses that LOOK vacant?

[Vonetta Booker]

I've been seeing a lot of homes during my recent "dollar drives" that *look* vacant (i.e. rundown, overgrown grass, no car in yard, etc.) --but I'm not sure if that's the case, or if it's actually occupied & the house is just plain ol' raggedy, lol. 

Is there a way to approach the owners to ask whether the house is vacant without offending them (in the event they still live there)?  And if they do, do you go ahead and ask them if they're still interested in selling? (Which I guess couldn't hurt since they're already on the phone, lol.)  

Any thoughts / feedback appreciated!