I would take the sponsorship they're offering. You're not obliged to work there for long after you've finished and it will look good that they sponsored you. They clearly want you to stay on. Given the way that the housing market is going it's a bad time to be cutting ties with potential employers. Also, if they're sponsoring you, they have an incentive to help you to finish. If it's getting too much for you, they're going to want to make sure you get through and I'm sure they'll be supportive. They don't make that kind of offer to just anyone.**