Questions for sellers

I am starting my investment career and have a few questions I need help with. The type of investing I am planning on doing right now is to either flip or buy and rehab (small rehab projects). The first question is what types of questions should I ask the seller when I contact them so that I will have enough information to investigate the deal further, prior to a house visit? The second question is what type of investigation should I engage in prior to seeing the property, during the house visit, and after seeing the property? I am also interested in where the majority of these types of deals come from? Should i check the local newspaper, the foreclosure lists, the MLS, etc.? The more detailed the answers the better.

I would also like to take this time to say that this is a terrific message board, that I have learned alot from. Thank you for your help.