NEW YORK (MainStreet) — Pick the odd city out: Chicago; Winter Haven, Fla.; or Newport Beach, Calif. And know such a place is where you do not want to even think about buying a home today.

Listen to the bubble watchers at real estate tracking company Trulia, and that is an easy challenge. Newport Beach - all of Orange County, in fact - is the one to avoid because, per Trulia, current home prices exceed what fundamental values say they should be by 17%.

That leads the nation in terms of real estate froth.

Trulia insists science backs its fundamental values. In a blog post, it explained what they are rooted in: "We look at the price-to-income ratio, the price-to-rent ratio and prices relative to their long-term trends."

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Find a town where incomes are low and, necessarily, housing prices will be likewise. If rents are low, so must housing prices. If they aren't, something - worrisome - is out of sync. If housing prices suddenly are shooting up after decades of stagnation in the area, that, too, is a warning sign of a bubble.

But just because house prices are high does not mean the town is in a bubble, said Trulia chief economist Jed Kolko in a Mainstreet interview. Case in point: San Francisco, where you have to be a dotcomer even to think about buying real estate (website Zillow pegs the median price at $971,600). But, said Kolko, Trulia numbers show Baghdad by the Bay is only 6% frothier than its fundamental values indicate the prices should be. That SOMA condo with an asking price of $1 million probably is fundamentally worth $940,000.

That's no bubble.

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Single-digit variations from the fundamental values, explained Kolko, are not necessarily a sign of a dangerous bubble - but even taking them into account, only 24 of the top 100 U.S. home markets look frothy, per Trulia's calculus. Of those, many are only very slightly overvalued (Dallas, Tex. and Sacramento, Calif. at +1% for instance).

How many metros are dangerously overvalued? And exactly where are the best buys in today's real estate?

The Trulia numbers offer guideposts.

The most undervalued homes in the nation are in the rustbelt - the once industrial midwest - where Akron, Ohio tops the chart at 21% below fundamental value. Cleveland, too, is 21% below fundamental value. Detroit is -19% and Dayton, Ohio is -16%.

Yes, but you want somewhere you might want to live? Feast on this: Chicago is 14% below fundamental value. So is Winter Haven, Fla. So is Providence,R.I.

Worcester, Mass. - 51 miles from Boston and home to Holy Cross and Clark University - is at -15%.

What's overpriced? Pretty much all of the Golden State. Besides Orange County at +17, Los Angeles is +15, the Inland Empire (Riverside-San Bernardino) is +13, San Jose is +11, and Oakland is +10.

Also in the top five are Honolulu - +15 puts it in second place - and Austin, Tex. in fifth place at +13.

If that sounds bad, know it is not good but it is nowhere near the froth that prevailed a decade ago. In 2006, Honolulu, per Trulia, was +41. Orange County was +71. Los Angeles was +79.

"Overvalued today is not what it meant at the height of the bubble," said Kolko.

At the height of the bubble, Miami was +80 - meaning that a hypothetical condo selling for $180,000 in 2006 might fundamentally have been worth just $100,000. Today, a Miami condo selling for $104,000 is worth around $100,000 (Miami is +4).

Are we heading back to an era of breathlessly high home prices? Not likely, not soon. Much of the nation's housing is tracking very close to what the fundamental values say the prices should be. Only seven metros exceed fundamental value prices by double digits.

Kolko, for his part, does not see the country hurtling into a new national housing bubble, because, he said, "housing prices do not turn on a dime the way stock prices do. A 1% gain or loss in a month for a metro area is lot."

That means it's a good time to buy. But probably it will still be a good time a year from now.

—Written by Robert McGarvey for MainStreet