What Needs to be Met in a Foreclosure?

[Peter Pezzano]

I'm starting to target pre foreclosures. This is the example I would like to be made more clear:

I find a seller who has received a notice of taking, I make him an offer to sell to me and he agrees. How do I know how much back money is owed to the bank? If their are any liens against the property, am I responsible for settling them? Is there a certain amount that needs to be met in order for the seller to be able to sell? Say he owes the bank 200K, do we only have to meet the 200K to have the mortgage be satisfied? 

Any advice is much appreciated, thank you.