Great question....I'm not sure any of us can answer accurately, because how do you know until you get there, have the right piece of property, etc.
Long term thinking I'm not sure it is great to build two homes on one piece of property. What I'm thinking is at some point down the road, what if one of you no longer wants to live on the property. Now you have a house that is potentially difficult to sell or maybe impossible.
I'd think buying two lots in the same area, or one big lot that you could subdivide into two separate lots or 3...maybe with homes each on 1 acre, and the other 4 acres separate that could go with ether house or be sold separately might be an option too.
Side by side comparison you can check out http://dfwmarketinsider.com/ and then click on the compare link.
You can also search for lots at this link: