Building 1 story vs. 2 story home?

I am a single mother of 2 small children, having just gotten divorced. I am getting ready to construct a new home, very small, only around 1500-1600 square feet. I do not have a big budget, BUT, everything in this area is WAY overpriced, so building is my only option. I am wanting the basic home, 3 bedrooms, 2 to 2 1/2 baths. I have not decided on a plan yet. I am wanting to take the least expensive BUT cost effective route. Is it better to build a 1 story home or 2 story home? Is it easier to heat/cool a 1 story or 2? I am planning on doing a lot of my own work, ie. painting, flooring, etc. Any other suggestions on how to save money?