Matthew McConaughey and his girlfriend Camila Alves are set to cash in on the birth of their baby son after agreeing to sell photos of him.The couple are set to receive $3 million (£1.5 million) from OK! magazine for exclusive photos of their baby son Levi who was born on Monday at a Los Angeles.The agreement is also said to include the baby's first Christmas with the family and will grant the magazine first rights to wedding photos, should McConaughey and Alves walk down the aisle.