How do you evaluate off market properties?

[Josh Green]

I'm a new investor and I've honed in on my methods for finding leads - drive for dollars, whitepages to get the phone number, etc. I've found a home that I believe can be a home run deal - a small house (roughly 750-850 square feet) on a property that is very evidently not cared for. It's close to other high end student housing in the area so I'm confident if I find the right contractor, I could turn it into a nice rental for a landlord looking for a good deal. My question is though, when I go to call the property owner, should I be asking if they're interested in selling and then if they are, proceed to for details about the property and/or to go take a look to confirm details? Or should I be ball parking a number in my mind based off of limited information, in order to be prepared to give a verbal price offer on the home? This question may be missing some gaps in terms of the sequence of the event, but all the same I'm just trying to wrap my head around it so I can proceed with action.

Thanks!