Start with what real estate pros call the "capitalization rate, " the return a rental property likely will fetch in the coming year, as a percent of its market value.

FORBES: I, Landlord

They can tell you how the value of any home stacks up against what it would fetch on the rental market.

FORBES

Tully says to beware of "bubble" real estate markets, where the price of a house completely diverges from the fundamentals that determine the value of a home personal income and rental rates in a particular market.

NPR: Avoiding the Housing Market 'Dead Zone'