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

Why are the gambling stocks so hot these days?-- Keith from Nebraska

James J. Cramer

: Why do you think? The house always wins! But seriously, these companies have a relatively stable level of expected margins. There has also been a lot of industry consolidation in the past year, which has sent many investors looking for the next takeover target.

While I don't usually like to chase momentum, the one stock I prefer in this group is

Harrah's Entertainment



I always see McDonald's (MCD) - Get Report restaurants in prime retail locations. Do you view them as a potential real estate play?-- Tom from Missouri


: Looking at the company's most recent


annual filing (10-K), McDonald's leases about half of the locations of its 15,000-plus restaurants. You're going to have to focus elsewhere to find a good land bank. That said, I don't like the new management team, so don't bother owning this blue-chip now.

My husband wants to invest half of our money in Costco (COST) - Get Report. Is that too much for one stock?-- Laura from Florida

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: I do not like to see anyone have more than 20% to 25% of their portfolio in one stock, no matter how good the company is. This goes for retirement as well as regular trading accounts. Diversification across different companies and sectors will allow your portfolio to perform well in many different market conditions.

Interested in more Cramer? Check out Jim's rules and commandments for investing from his latest book by

clicking here

. It's a series of articles from Cramer on how to become a better investor. The following table lists some of the rules that Cramer dissects.