I guess I'm confused. Who is selling the house? How was the $189K asking price conveyed to you. You want to offer $55-$60?
Play along...
Your sister: "Hi Daniel. I just listed my house with XYZ for $189K. My realtor thinks it may be a little high, but we think we've already discounted it for some repairs I think it will need - probably $10K."
You: "Well sis, I've looked at the house and it really needs $25K. And I think your $189K is optimistic if it were already fixed."
Sister: So you are saying its really only worth $164 tops as it sits?"
You: "Yes, I'm afraid it is. And don't forget, someone buying it will still want a little more discount to account for the time and risk of fixing it up."
Sister: "Wow, so if my 189 should be only 180 and take off 25 for repairs and arbitrarily another 25 for risk etc, I can only expect $130.?"
You: "Yes - I'd say that's about as much as you will get."
You: "But wait, I've got a great idea. I can buy it from you and rent it out. After my calculations I think I can offer you $55 - $60K - after all, taxes, and ins, and maint, and lawn, and vacancies are pretty high ya know."
Sister: "Oh Daniel, You're such a sweetheart. I'll take it!!!"