Mad Money Mailbag: Careful With Modular Homes

Editor's Note: The following are questions received from viewers of "Mad Money," seen every day at 6 p.m. EDT on CNBC.

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With the crisis following the hurricane, modular homes seem like a solid investment. With that in mind, is Coachmen Industries(COA Quote) a good investment?

-- Brian from New York

James J. Cramer: I believe you have a viable idea. But note that Coachmen and many of its peers derive the majority of their revenue from recreational vehicles.

Because of that, I believe Coachmen will be more affected by the negative of astronomical gas prices than the positive of a sudden demand for its housing products.

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My wife has about 80% of her portfolio in IBM(IBM Quote). Should we hold it or sell it?

-- John from Texas

James J. Cramer: Whether I like IBM or not, I believe you need to sell at least half of your holdings as soon as it makes sense for you to do so.

One of my basic rules for diversification is that no one stock should count for more than 25% of your portfolio at any given time.

It does so happen that I do like IBM's prospects over the coming quarters, along with the technology sector.

Even so, investors are taking an unnecessary risk by placing all of their chickens in one basket.