I'd honestly go through a humane society, or a dog rescue if you want to "know what your getting"
Honest truth is its going to be next to impossible to tell if they are giving away the dog for a good reason or not. "I can't give her what she needs" and "I don't have time for her" all are
red flags to me. I have a full time job and I can give my dogs what they need.
That said, I have 5 dog that are owner discards. If you are willing to put in the time and patience you can fix most if not all "problems" but its tremendous work. Probably better to go with a dog with a know history thats over a year old.