Editor's note: The following are questions received from listeners of "RealMoney Radio." To send Cramer a question about topics from his radio show, click here. Listen to Cramer's latest radio show by clicking here.Is buying a house a good investment? -- Cory Jim Cramer: I have always believed that a house is a great investment, but only if the buyer plans to live in it for a long time. Buying a house with plans to flip it in a year or two is just as speculative as buying high-flying momentum stocks on margin, and requires a heck of a lot more paperwork and headaches. Why are the big oil stocks so cheap? -- Brent Jim Cramer: The big integrated oils like Exxon Mobil ( XOM)trade at low valuations mostly because energy has historically been a very cyclical market. In addition, the major oil companies are having an awful lot of trouble finding meaningful amounts of new oil, making it tough for them to grow earnings. Want more Cramer? Check out Jim's rules and commandments for investing from his latest book by clicking here.