House with major structural / foundation issue on a sliding hill

[Han Oh]

I got a call from a seller today who has a 1300+ sq.ft. house that been vacant and yellow taped for some time. The house sits on top of a hill, giving it a nice view, but that is giving way and sliding off. Half of the backyard is literally hanging off of the cliff. There are visible cracks along the floor of the dining and kitchen areas (as you can see from the pictures). The city is currently evaluating plans for soil reconstruction and remediation. 

Seller owes $60K of back taxes (has not paid taxes for the past 6 years) which I verified via county website and has a lien worth about $5K according to him. He says he will sell the house to me for $80K with him taking care of cleaning up the title. Property is in a nice area of Orange County, CA and could be valued at $600-700K after repairs and of course soil remediation. Sold comps around the neighborhood run between $700-800K.

Being that I don't have a lot of experience yet, I don't have any idea how involved and how costly (in terms of money and time) it will be to bring this house back to normal and up to par with other properties around. 

Is there any investor out there who works this kind of a house?