What is your best strategy to renegotiate a sales price?

[Clay Sexauer]

I currently have a property under contract at $135,000, rehab is $30,000 and my ARV is $235,000. After doing my due diligence, I want a bit more wiggle room in the rehab, simply for the unknown because the house is 60 years old. If I go back to the seller with an offer of $125,000 (due to the amount of rehab), what are some successful strategies you have used to get the seller to come down on the sale price?