He currently plans to walk on at Texas Tech or attend a Division-II school such as West Texas A&M and Northwest Missouri State, according to a source with knowledge of Mark's plans.
Mark, who rushed for 1,366 yards and 12 touchdowns in 2012, is one class short of graduating, which means getting a waiver will be challenging. Otherwise, he'd likely be attending Houston in the fall.
Texas Tech is a possibility because Mark's mother lives in Lubbock, which could facilitate a waiver, but Tech told Mark's camp it's maxed out on available scholarships. Texas also said no because Charlie Strong is cleaning house and isn't taking on new players at the moment. Walk-on status is still no guarantee the NCAA will grant the waiver, but he might have a case because of his mother's location.
Unless an FBS school can circumvent NCAA eligibility issues, Mark's likeliest path is playing D-II ball for a year, then heading to the NFL draft. Mark's camp has talked to West Texas A&M and Northwest Missouri State about playing there. Mark can play for a D-II school despite having one year of eligibility.
Mark missed most of the 2013 season due to injury and left Northwestern shortly after the team announced a two-game suspension earlier this month for violation of team policy.