Depends where you live. For example, it'd be weird if you have no iron in Virginia because of all the red clay (we had so much iron in our well water that it would actually precipitate out when we boiled the water or took a hot bath!). You can get an idea of the presence of iron by looking at the color of your soil. If it's bright orange or red, you'll have tons of iron.
I'd think a lack of phosphates is to be expected unless you live very close to active, large-scale farms, a peat bog (or the equivalent), or a very large compost heap. Possibly a large forest too, now that I think about it (decaying plant material produces phosphates).
Another thing to consider is that most wells have to have the water tested for harmful things like phosphates. We had a bunch of 6' x 8' x 10' holes in my now-front yard for a year in order to test the water (among other things) before they could dig our well.