House is broken

So the house that we are trying to get is broken. OK well the septic system needs to be replaced. So we are trying to cut a deal with the seller that will save us money in the long run. It seems that most of the houses in that area have messed up septic fields. So I guess we have till Monday to make a decision. I believe the sellers will take this up as they will never sell a house that needs $15,000 worth of work in order for it to be habitable. So we make our offer more, meet them in the middle 1/2 of $15,000. So instead of just offering $50,000 we offer $57,500. Which is still lower than what their asking price is,and for a house that I absolutely love and with 5acres of land, I mean really it's not bad especially when they house was appraised for $69,000 and that was without the 5acres. So now we have till Monday, and Harvey is kind of wanting to walk away from this house, but I don't! I really don't! So I think I will have Harvey talked into the slightly bigger offer for the house, which even the realtor and loan officer said, it would be worth it because the brand new septic system would last decades! :D