What are you flying? Just as in full scale size makes a difference. An Ultralight doesn't need the same room as a 787. Parkflyers don't need the same room as a 40 size trainer or a big gasser. I fly my quad in my backyard all the time and my total acreage is 1/3 of an acre. I could fly a Snowball back there too except for Juice the conqueror, Juice the destroyer, Juice-Killer of butterflies and Juice, idiot dog who things everything that flitters around in the backyard is a butterfly. With the exception of quads which have biting rotors on all 4 corners. He STILL nips at those from time to time anyways.

I'm looking to move to a house that has 4 acres, I'll be able to fly most of the flite test sized airplanes there un-impeaded. But they don't take that much room up anyways. The house I'm looking at also has room for a 200 foot control line circle. The nearest house on that side is a quarter mile away. Nearest on the other side is 150 yards. Proper use of flying time will make CL in my yard quite enjoyable.

The Local RC club field is 15 minutes away so anything larger can be flown there.

So, it matters what you will be flying. Your experience level may add in there too, little bit.