Here are three stocks with buy rank and strong momentum characteristics for investors to consider today, September 12:Mr. Cooper Group Inc. (COOP) : This mortgage servicing company has a Zacks Rank #1 and witnessed the Zacks Consensus Estimate for its current year earnings increasing 5.2% over the last 60 days.Mr. Cooper Group's shares gained 5.5% over the last three months compared with the S&P 500’s advanced of 2.8%. The company possesses a Momentum Score of A.Affirm Holdings, Inc. (AFRM) : This payment p ...