Kurtis is right; your friend should read his loan documentation. Second-home financing generally includes a disclosure that affirms that the property is a second home, will not be rented for more than X days out of the year, and will be lived in for at least X days/months out of each year. It is possible that if the lender determines that the home is actually being used as an investment property, the loan could be considered due and payable. In this worst-case scenario, your friend may have to refinance into an investment property loan.However, here in Colorado lenders are not in the habit of checking up on usage. As long as he initially used the property as a second home and pays his mortgage on time, it is likely that the lender will never discover his misrepresentation.Of course, misrepresenting your intended use of the property on the loan application is not ethical nor is it legal to my understanding. If the home is a second residence that he rents out between uses, then second home financing may be appropriate. However, if you purchase a property purely as an investment, you should indicate that usage to the lender.