I mean, you wouldn't have to worry so much what neighborhood you drove through with one of those...
Current FedGov policy will not allow armored vehicle sales to non-governmental agencies without demilitarization. If Joe Jones wanted to buy a surplus MRAP, he'd be required to de-mil it (although I don't know to what extent). A county sheriff's office or city police department could get one for a very low price or maybe even donated to them. In any event, the typical MRAP is nothing but a wheeled armored personnel carrier — an armored truck. They get stuck easily, they're very top heavy, blind as a bat when closed up, clumsy vehicles, and very expensive to maintain. They are vulnerable to improvised weapons as primitive as a Molotov Cocktail.