Flip/Rental Opportunity in a Great Location

[Kevin K.]

We found a great property right by the beach that has been on the market for almost 300 days and multiple price drops.  The lot is around 3500 square feet.  I am not sure that the property could be renovated and would like to understand full renovation costs vs full rebuild costs.  It does have a basement and sounds like a deal fell apart because of a beem in the basement..  Didn't get the full details.  

The big questions are what does a full demo usually cost,  what might I expect to pay to build a economical 2/3 story beach house.

When would you walk away from a deal?  We would pay cash for the lot and then either get a loan to build or pay cash.