I think this is a problem that many horsey college students face, unfortunately. I know of several students in your same boat but who have found ways to continue riding. They get jobs - whether at barns, as waitresses, or whatever they can get - in order to pay for their equine hobby. They then lead very self-disciplined lives, fitting in a rigorous liberal arts education, maintaining GPA's above 2.65, keeping a job, and riding. I don't know what opportunities are available to you, but I would suggest using some time this summer to explore those options and then do your best to save money. If you're unable to purchase your own horse right now, you can at least take lessons on another horse.