Approaching an owner that is not actively seeking to sell property

[Brandon Lee]

Hi All: 

I am seeking advice for the following scenario: 

I bought my first two rental properties this year and there is a property that is "abandoned" (not currently occupied) next door that the owner only uses to store stuff in the backyard.

It is not a legal duplex, but it does have two apartments (one is an accessory dwelling unit, so requires that the owner occupy one of the units). I am interested in purchasing the property and flipping it. 

My property manager has spoken briefly to the owner (saw him next door one day) and he expressed some interest in the possibility of selling it. I should note that I have not seen the inside of the property to date.

Two questions: 1). How do you suggest I go about contacting the owner? Any particular strategies you suggest? I have used a realtor to purchase the other two properties via the MLS, but this is not even a listed property and I am interested in pursuing this one myself.

2). Can you provide some advice regarding valuation of the property? I have information from the city regarding property valuation, but not sure how accurate that is. Can you provide some thoughts regarding how best to go about this? 

Many thanks in advance for any help!