How much to offer on off-market property?

[Eric P.]

I'm about to reach out to a home owner, best neighborhood in the area and this house looks a little forgotten about.  Doing a bit of research it looks like the owner is 69 years old, "purchased" the house in 2003 for $100, so I'm guessing family gifting.

The estimated purchase price online is about $315,000 so if I'm correct you offer 70% of the price minus any repairs.  Assuming it needs $50,000 in repairs/updates that would mean I'd need to be under $170,000 on the property is that correct?  

I'm also very risk adverse, so if it's estimated value is $315k I'd assume $300k and if I thought $50k in updates I'd probably go with $60k in updates to be safe so then really I'd want to offer $150,000.. Do deals like this actually happen?

This would be a buy and hold.