Bern owns three homes.
Sanders is hiding some of his assets (legally):
O’Brien says that Sanders’ financial disclosure forms are incomplete. “For someone who doesn’t care about money, he goes a long way to cover up his true net worth,” he says. “Bernie does not disclose the value of real estate holdings. He can. He is not required to, but he could if he chose. It is known that he and/or his wife own at least two homes—one with rental income in Vermont and one near Capitol Hill where the median home value is $722,000.”
According to FEC rules (or maybe it's the Senate ethics rules), if you are collecting rental income on real estate, you are required to report the value of the asset and the income, although it's a range rather than specific value.
Only personal residences that don't generate income are excluded.