Welcome to Pond Boss!

Part of your due diligence is to look at the dam of the main pond and the smaller pond. Does the largest dam look like it has been blown out by a flood and subsequently repaired? That is your most difficult/expensive thing to fix as a pond owner. If it hasn't blown out previously, then you are probably good to go. (If the upper pond is a groundwater pond, then the surface watershed feeding water to your ponds might be quite small. That greatly reduces the risk of a dam blowout when the remnant of a hurricane drops a deluge of water on your property.)

Next, are there trees on the dam? If so, they will eventually work very hard to cause a leak in the future. If there are big trees and you cut them down, then the dam might start leaking when the roots rot.

Do you have a tiny boat or puddle jumper? You can easily survey both ponds with a 10' stick of 3/4" PVC pipe. Determine your deepest parts, and your average depths. Also, you can feel the muck with your pipe. A clean bottom should feel "firm" and you have to work a little more to push in the pipe. For example, it could be clean, saturated sand. Also take some heavy string with a weight if the owner thinks there is some water deeper than 10'.

I don't like the muddy water. Is that in both ponds? Have you had recent heavy rains? One of the main reasons for muddy water is some type of fish that constantly stirs up the bottom of the pond. Carp/koi, bullheads, other types of trash fish? All can be dealt with, but might be some work before you can create the type of pond you used to enjoy for fishing.

Good luck on your property purchase and your new ponds!