@Acre4Me - I googled it & a couple sites said they have very large root growth & should be planted 20 feet from a house. Also read they can destroy sidewalks, driveways & other plants in their way.
I've only grown them in pots as they may survive a couple winters here, but they wouldn't survive them all so I've not ever seen their root growth outside.
@TJAnonymous - my grapefruit spends the winter in the sunroom & that gets down to 32 regularly & it does just fine. The biggest shock for it is direct sunlight outside, I've burned the leaves on it a few times just throwing it back outside because once it's out it ain't coming back in! If I expect a frost for a night I just cover it. It's over 35 years old & still kickin no matter how badly I treat it, lol.