As stated by several, buying the whole kit is less expensive, and there is a use for all four walls in any bashing project like these here.
As soon as one gets comfortable with cutting panels the possibilities become endless: you can cut out doors and re-position them, alter building width.
I often add a small styrene foundation only 1/8 to 1/2 inch tall, notched or scribbed as if stone blocks, to slightly raise elevation to vary building height.
I depend very much of a small ($135 range) bandsaw when doing this work. I use a fine toothed, metal cutting blade to get a precise, clean edge: it still cuts through Ameritowne panels like the proverbial hot knife through butter. The edges of the bricks provide a very straight cutting guide so you can slice and "edit" the panels and keep edges true.
It is as if they were made with bashing foremost in mind.