its pretty common. when shopping for my 08 in March, the first one I looked at (private owner) was white, clean as a whistle. Then I noticed a little orange stain on the plastic rocker, the lady said its just the running board. Well, being plastic I knew better and put my finger through the rocker.
Next vehicle was at a Ford dealer. I called on it, asked the salesman about rust on the rocker, he went and checked said there was none. I went and looked at it, same thing, put my finger through the rocker and pulled up a chunk of rust and gave it to him.
Finally found a solid one but it took some looking.