I make sure my clients offers are all legibly typed out, neat and easy to read, with realistic time lines based on the type of funding they have and due diligence they need to perform.  

Yes, it is not legal to cancel the contract based on the new offer, but nothing stops the seller to change the closing date or whatever is in the contract (except the purchase price, of course, this attorney can not change).

The second loan would be a 30-year fixed lower interest asset-based non-recourse loan.

@Christie Duffy  Very much depends on the end product quality level.... as @Jim Adrian mentioned, $125 per SF has been a base number we've used for new construction though my experience is in the burbs, not urban Hoboken.

If you want additional money based on the current value, you would have to be on title for 6 months.  

I am based in Silicon Valley and my associate is based in Chicagoland. 

That way, even Bargain Hunters will be suitable for your Buyers List!

You mention the owner has paid $70k on the mortgage but that isn't a number that matters (since who knows what interest rate he's on or if he's made any extra payments), what matters is what the outstanding balance is on the mortgage and can you offer them a purchase price that is A) Fair to the owner, B) Helps them sell with some amount of equity and C) Gives you room that it financially makes sense.The numbers change based on if you want to flip it or rent it, making the question "does it make sense" different based on the direction you choose.In short, I have no idea how much I would offer...

I also like to determine a ball park price/square foot amount as a screening tool--based on the average rental rate in an area.

It might be more of a concern in a complex dominated by owner occupants, who would be more likely to push through HOA rate hikes that are less likely to see a net gain for an investor.Your cashflow is entirely based on how much down payment you bring to the table and terms of the loan.