Got to agree with the practice. Its even happen in the city apartment. Say for a 3 bedroom unit, the main tenant lease out all the 3 bedrooms and collected higher rent. Whereas she/himself live at the dining room or a removable cubicle in the living room. After deduct the montly rent of $650/week, he/she still pocket around $100+ a week.
From a investor point of view, he don't need to bear any risk of mortgage, rates, tax. Its free money from sky.