Good advice on this thread.
I'd add a few other things that I feel are important but not really pond-related.
1. When you do find a piece of property you're interested in, talk to the neighbors. It will give you a feel for the area and how you might (or might not) get along with everyone.
Some folks are just hard to get along with.
2. Think about ease of access to the property, ingress and egress in bad weather (floods, winter, etc.).
