The listing agent also doesn't have a chance to size you up, if you're new full of guru ideas, that's another plus.

If you have window units and/or zonelines, they're not going to condition the house as well as a properly sized central gas system with correct number and location of vents and returns.

citydata.com is a great resource to get an amazing array of information on demographics, employment, household size, commute times, bedrooms/unit, property type breakdown.. all census data and more.. 

Even if you talk them down to being OK with only $10k in profit, $15k sounds VERY low for rehab costs on a house that size, unless it is already nearly move in ready.

Is your competition house reflective of all rental houses that size and price point or is that house an outlier?

There is actually a pretty good-sized network of people with experience in Central Mass, but I'd be happy to share any experience I've gleaned too.

The rub is that they usually will only command 650-725mo. due to size & location.

Hard to really understand what the overall issues are without much more detail but in every project you can have typically two of the following:Scope, Schedule or Budget....Sounds like a substantial increase in SF where the property is doubling in size.

., but it can be the size of a business card.

..1150 sq ft is a nice size, but be careful not to overpay if 3br not an option..