Caltech accepts only 15% of the applicants (2009 data), so yes, it is pretty hard to get in. However, there are other schools that are even more selective - such as: Princeton, Stanford, MIT, Annapolis (Navy), Ozarks, Yale, Cooper Union, etc. - and quite a few Nepali students go there. So don't be disheartened.
If you have the chops - high grades, excellent SAT/ACT scores, stellar recommendations, stand-out essay(s), extra-ordinary extra-curricular activities under your belt, etc. - I say you should apply. As for money, no need to worry. Caltech will make sure that you can attend if you get accepted.
Given the fact that very smart kids go to Caltech, of course, the level of courses and competition will be quite rigorous. Unfortunately, like Harvard, Caltech is knows for it's "sink or swim" culture. Some kids do well in this environment, some don't. In that regard, Princeton University is known to be most supportive of its students. It is equally hard, if not harder, to get into Princeton. But once you are in, they make sure that their students don't fall through the cracks.
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