The owner is concerned that one tenant wouldn't be able to pay the complete payment but may not move out when the rent isn't paid in full. Even if he can expect to be able to legally go after any or all of you to pay he can decide if he wishes to deal with it. Getting money from someone who doesn't have money is hard.
Lenders often have a similar criteria. If either a husband or wife has a terrible credit score while the other has an excellent score, the loan may be more likely approved if only the borrower with the excellent score applies for the loan.
Sunnyvale real estate information at http://julianalee.com/sunnyvale.htm
Top 2 agent nationwide at Keller Williams Realty, the nations largest
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Over 1,000 homes sold in Santa Clara County and San Mateo County