Financial considerations aside, I would first make a choice between LAC or research university. If you think you may want to focus on one major, such as math or physics, LACs are a poor choice because you will run out courses very very quickly.
At research universities, it is common for the stronger math and physics majors to start taking graduate-level courses in their junior year. That’s simply not an option at a LAC. Math + physics majors at LACs also fare notoriously poorly in admissions to selective PhD programs; PhD programs use the advanced-ness of an applicant’s coursework as a proxy for their potential in graduate school, which puts students from a LAC at a huge disadvantage.
Don’t just take my word for it. Swarthmore’s math department is telling their students up front that they’ll be at a disadvantage when they apply to PhD programs simply because they attended a LAC: http://www.swarthmore.edu/Documents/academics/math/grad_GRE/MathGradSchool.pdf
On the flip side, LACs may work much better for you if you consider yourself shy. In my experience, all of the opportunities available at LACs are also available at a research university, but they are much easier to come by at a LAC. A few examples: At a LAC, professors will notice you and learn your name just because you’re in their class. At a big university, you may have to make a point of going to office hours if you want to be noticed. At a LAC, professors may approach you about summer research opportunities. At a big university, you’d have to approach your professors. At a LAC, you will naturally get to know your classmates because you’re taking all of your major courses with the same group of 10 students. At a research university, you may have to work a bit harder to make friends.
I personally attended Bryn Mawr, another LAC not too far from Swarthmore. I really enjoyed the LAC-feeling for the first two years, and then I wished I was at a larger university with more opportunities. I ended up spending most of my junior and senior years at Penn taking graduate courses, for which professors at Bryn Mawr gave me independent study credits. However, I should point out that this is NOT a standard arrangement and Swarthmore would NOT allow it. (Swarthmore is much stricter than Bryn Mawr about breadth of coursework.) On the other hand, I am grateful that I started out at a LAC. I was painfully shy when I started college and I would have gotten lost in the crowd at a big university.
You’ll have to ask the colleges directly if this is possible. Most colleges and universities will not consider international students for need-based financial aid in future years if they did not apply for it at the time of admission - that’s because they don’t want applicants to apply without financial aid, use up all of their savings in the first year and then rely on university funding for the following years.
Many colleges will have merit-based endowed scholarships for returning students. These are usually small (e.g. $500 for an outstanding junior physics major) and are often not advertised on the university website.
I would strongly encourage you to make your decision assuming that you will have to pay the full cost of attendance for all 4+ years.
