Assignable Mortgages and creative financing

[Connor Deneen]

Hi everyone, I am trying to learn a little more about assumable mortgages. I have a potential deal where the seller owes 100k on the property and their mortgage is assumable. All other factors taken into consideration (all the numbers work out well), my questions are as follows:

1) If purchase price ends up being  100k, and I took over their mortgage,  what costs would I as the buyer incur.

2) If we agreed to a price lesser that's 100k, who would pay the difference in what they owe?

3) To avoid down payment, could I, as the buyer, agree to terms that state 100k as the purchase price but with the seller paying say 10k out of pocket to the buyer for repairs or something along that line?

4) Do you have any other suggestions about how to negotiate with someone who owes the amount of, or more than the desired purchase price?

Just trying to learn a bit more, thank you in advance for your insight everyone.