His $20 million mansion has a moat. Of course it kind of makes sense as Yahoo! Sports puts it.
And the moat should keep the mounted infantry attacks on the Patriots quarterback to a minimum, which should help Bill Belichick sleep better at night.
While Brady is extremely well paid, Gisele makes even more than he does (some have called her the last of the supermodels) so I am assuming the mortgage payments are going to be made. That being said I remember being in Boston when he was first starting off his career and they had this magazine article about how he was just like everyone else. I am just assuming that this is no longer the case, unless moats are much more common in your part of the world than they are in mine.