 This is House Call for Health. Anyone who hopes to become a doctor has new incentive to choose Johns Hopkins University, where most medical students will no longer have to pay their own tuition, thanks to a billion-dollar gift from Bloomberg Philanthropies, whose founder, Michael Bloomberg, attended the school in the mid-60s. The gift begins paying tuition for medical students starting this fall, as long as their families are earning less than $300,000 a year.