For a really good look, spend a few extra dollars and get a squared off stainless sink; something like thisI've heard of granite composites cracking and chipping after only a couple years. 

However, if you are looking for the cheapest solution, a treated 4x4 or 6x6 square post is the ticket.

Each building has extended about 100 square feet for creating a laundry room.

But, those are, from what I hear, full of lots of red-tape and tiresome logistical processes, so you might just be better off going with the low-down payment loan anyway.  

Its relatively affordable and the price per square foot quotes I'm receiving  would allow me to secure something in my price range.

The BPI analyst aforementioned can actually tell you how many square feet your home is leaking through performing a Blower Door test (what @Justin Fox was referring to) before and after air sealing to see how well they did. - Is the water heater propane as well? 

While the state government may have created red tape/permits specifically for real estate, there is not a statewide general business permit.

Also you might be able to add a 2nd floor if the footing can support it, if it's a problem of not enough square footage...that may be cheaper than a tear down but probably not if it is really old or in bad shape...

Moreover, Bank appear to only want to deal through a real estate broker, which is also hard to find due to the red tape associated with these type Loans they shy away including the financial institution.  

Is there a rule of thumb per square foot on how much this should cost?