Vacant Lot Comps - please scare me away

[Eric Olsen]

As a result  of my direct mail, I am working with a seller on a land deal in Westmont Il.  Here is what I know....

Lot size 50 x 150

Utilities are available 

Sellers asking  price is 97.5K (I know sellers asking price is irrelevant)

Seller needs cash to pay off about 40K in debt and 25k to rehab home.

Here is how I comp'd the lot. I figured the Sq Ft price for lots sold in the area of similar size then averaged them. I used that average to get the valuation of the lot. 

My valuation of the lot is 53K.

Using 70% places max offer at 37K. 

Homes on this same block have an ARV approx 250K to just below 300K.

I called the seller yestersay to inform him that my research was pointing to  the lot being worth less than what he thinks. I did not give him any numbers at this point. He still wants  for me to make an offer to consider. Clearly has some motivation.

My thoughts are to offer 32K and see what happens. 

Please scare me away from this deal with something  I missed. 

Lastly please excuse any weird verbiage or spelling. This was posted via mobile. 

Thank you, All!