So...how do I do this gap year thing?

There’s a saying, “if it was that easy everyone would be doing it”. People would be moving all over the country and from different countries. Not worth the time and expense and as stated your not understanding what establishing residency is. But it’s good your asking questions and educating yourself before doing this. How about reaching out to the school or just look on their website to see what the definition is?

http://www.schev.edu/index/tuition-aid/in-state-residency