You should be able to find some historic data on appreciation rates for the Greenpoint area to support your estimated appreciation on a pro forma basis.As a side note...estimating appreciation is a great exercise, but there is much more to consider on an an asset and project of this type. 

PROFESSIONAL INSPECTIONS AND INSPECTION NOTICES: Buyer may conduct at Buyer’s expense (unless payment for such expense is otherwise required by governmental regulation) any or all of the following inspections of the Real Estate by one or more licensed or certified inspection services: home, radon, environmental, lead-based paint, lead-based paint hazards or wood-destroying insect infestation, or any other inspections desired by Buyer in the exercise of reasonable due diligence.

Instead, you can go on the internet and learn about effective exercise, buy a few workout tools, and do it right in your own home.

After I exercised my option a few months later and sold the house to another person, I told my mentor all about the deal.

The seller's story is that it was under contract before, the buyer's financing fell through and they exercised their right under the financing contingency to back out without losing their earnest money.

The focus that results from that exercise will help stave off the shiney nickel syndrome and should lead to more productive use of your time.

The evaluation exercise and offering is great education.

The Catch-22 is in the small print which leaves the exercise of this assumability at the discretion of the bank.

It also should be in line with the analysis that you did in the first exercise above.

They have equity and when they exercise the option, I'll get the last 20K.