Sample Goals

I plan on building an airplane this summer. My goal is to make it as cheap and practical as possible. So, my questions are:

1. Is PVC pipe a strong enough material to build the frame for the wings out of?

2. How powerful does my engine need to be (on the propeller)?

3. How important is the center of balance for the plane? If it is important, where should it be?

4. Is there anywhere that I could download some free sample plans to get an idea of what I am doing?