This could potentially double the legal square footage.  

Purchase Price: $ $265,000Equity: $18,000Current Appraised Value: $280,000Square Footage: 2150Mortgage Payment: $1,745Property Taxes: $449.14Insurance: $44.17Current Monthly Rent: $1,250Backstory: I was forced to move from the home due to a change in my employment and could not sell the home before moving.Current Situation: The current tenants were planning on purchasing the home in December, but have now changed their minds.Desired Outcome: Have the home sell as quickly as possible.

You should really do your homework on the value, preferably by square footage pricing, of the properties in the area.

The realtor that showed me the property only found two properties, one with less square footage than the subject property and the other with different characteristics (the subject property is a 3/2 and the other comparable was a 3/1 with a 10% overage on square footage.

As I understand it now, I cannot force as much value on the underground footage as I can on the above ground footage through improving the property condition...Anyone have experience with this?

I haven't seen a fire damage rehab, with similar square footage, that could be done the right way, for less than 40K,  so you are probably on track, depending on status of the HVAC.

Get info from the city like total building square footage and Owner information.

Comps on the vacation homes might be based on the recent local sales nearby which bring the numbers down - appraisals don't always take into account views, quality of constructions, etc, mostly based on square footage. 

We found a fixer upper 3/4 of a mile to the beach with more square footage then most rental homes.

You can have a Realtor put you on an auto feed from the MLS.You choose the criteriaZip codesSq footage# of baths# of BedsPrice rangeREO/Short sale/Owner owned etc.Then every property that fits your criteria is automatically sent to you.