Sometime in the future, there will be a new innovative design that will replace the current open floor plan trend, but it certainly will not be anything resembling what we had back in the 70s and 80s.

For example look at the zip code you are building in, for a recent new build in columbus that we do since miami is expensive we pulled all these stats: Zip Code Statistics: 43206Housing Units Delivered: 8 Average Sale Price: 642,875Median Sale Price: 505,000Average Price Per Sq Ft: $316.40Average Square Feet: 2172 Sq FtAverage Bedrooms: 3.25Average Bathrooms: 2.75Average Days on Market: 138We design the house around this, around the lot, around the neighborhood, from scratch and try to pick a long term build design that will do well.

The 4 bed vs 3+den designation won't have any effect on the home's value, or the rental income.

With that information you can then adjust based on your design's location, size, complexity, and finishes, subtract off what you think your materials savings are, and then voila, there's your estimated labor cost.The cost/sf question gets asked all the time on the BP forums so there are already a bunch of responses out there.

It's designed for investors at all levels—novice, intermediate, and expert.

Must have a smoke detector in bedroom.If you're not on town sewer is the septic design capable of handling the "extra" bedroom? 

@Jonathan Quintanilla:  Yes, there are several products, designed for larger/fewer #'s of units.

As for materials and the such, are you using an interior designer or using the interior of comps in the area?

The current measures are designed to ensure long-term stability and prevent the kind of market collapse seen in the past.

Interior designer here.