Wow you really have caught "the gardening bug!" Personally, I prefer to start with "a clean slate." A house with existing landscaping that I want to change would be a lot more work. It's a lot easier to make a new bed where there is now grass than to dig out shrubs.

You'll probably also want to have houseplants and "save" annuals that are actually tender perennials, so south windows that aren't shaded or are only shaded during the summer by deciduous trees would be appealing in that regard.

I also like a yard with a less-visible spot for a compost pile. My Mom has a nice yard on a double lot but since it's on a corner, there's no place in the yard where we can hide a compost pile without building some type of fence. That's an ongoing discussion.

Shade vs. sun. As far north as you are, sunny spots would be very important to me. A lot with a ton of huge trees and mostly shade would severely limit your range of plants.

Other difficulties that would be easier to avoid then deal with: big walnut trees, properties that would have browsing deer, slopes are hard to garden, untended meadows or weedy areas nearby can cause a lot of extra weeding work and would have a lot of groundhogs.

Is that the kind of thing you were looking for?