This OpenSCAD customizable thing can make a large variety of buildings. It is sized for an N scale model railroad layout but can be used with a variety of models.

Each side is configured in the Customizer and than created individually. You can vary the number of windows horizontally and vertically. You can add a door. (The door will be double wide if the number of horizontal windows is an even.) You can add a decorative roof line. And you can add a brick texture if you want. Also note that while the rendering in the Customizer is not perfect, the STL file that is created will be fine.

The roof is a separate thing and is called "Customizable Modular Building - Roof." You can find it here: http://www.thingiverse.com/thing:307520

If you are adventurous, download the OpenSCAD file and check out all the variables that can be tweaked. An example of what you can do just by changing a few parameters (and no code) is the Office Building found here: http://www.thingiverse.com/thing:312937

Update: I added some photos of one of the buildings fully painted.

I used the following settings on my MakerBot Replicator2 to print this design in PLA. I didn't use a raft and support is not needed.

Infill = 10%
Layer Height = 0.200
Shells = 1
Feedrate = 40
Travel Feed = 55
Temperature = 220

Once all the sides are printed, you will need to assemble them into a building. Here are some tips:

• Use cyanoacrylate (Super Glue) to glue sides together
• Lightly sand the edges to remove any burrs before gluing
• Inset the sides so they are flush with the edges of the front and back (this is assumed in the sizing of the roof)
• Glue the sides together first and then save the roof for last
• Expect to sand the edges of the roof to fit snuggly inside the four walls