I think it is great that you are beginning to think about these things while you are still a sophomore.
A back up plan is excellent, and you should always have one unless you are studying in a field that has an almost 100% guarantee for employment. Personally, I'd recommend something like music education. Besides the general teacher-related perks (a 9 month job with free summers, job security, competitive salary, etc.), you'll spend a lot of time in the music building, which could help your aspirations of becoming a professional musician.
When choosing your undergrad program - if music is your end goal, remember that all majors are not the same. Certain subjects are much easier than others, e.g., political science & communications vs. electrical / chemical engineering. That said, certain course loads will not allow you to take a minor in music, with respect to the time required for both subjects. I had a music minor at University of Delaware (major in chemical engineering), and dropped it after my 3rd semester. I simply didn't have enough time to maintain the private lessons, practicing for orchestra, etc. at an acceptable level. Also, some academic programs / majors do not accept music classes as electives - something to keep in mind. I took the 1st year theory course at UD, but it did not count towards my degree requirements. A great course & I learned a lot, but had no value in the engineering department.
W.R.T. tuition - for most schools, you can attend a school as an out-of-state resident and pay out-of-state prices. If you establish residency within that state for at least 1 year, you may qualify as an in-state resident, with lower tuition. Make sure to read the rules carefully - the rules at each school may be slightly different, regarding residency & residency requirements. Make sure your folks are on-board with the ideas also, as they may be footing a portion of the bill.
Keep playing as much as you can and have as much fun as possible!
Ian