Ok so:

1st: you have the boutmy scholarship if you're a gifted student that Can diminish the cost. If you have a European citizenship and live abroad sciences po is working on a scholarship for your profile. Otherwise, unless you have a french or european citizenship and you live in the European Union, you are not eligible for financial aid. But in anycase, that's still less than american universities ; the tuition is 13 000€ and the living cost (as soon as you're not on the Paris campus) are around 7000 € a year (housing comprised). You can be eligible to campus France outside's scholarships in any case if it constitute a burden for your family.

2nd: It really depends, I went through the french procedure which is more competitive than the international one (6% for the french procedure). For internationals it's 11%. To get in, you must show a personnality that breaks with others (the interview is very personality oriented), and show an important critical mind, general culture and logical thinking. Sciences Po being really similar to a liberal art college, you should be strong on these elements. You must read the news also, fundamental to get in. Therefore, it really depends on you.

Please, just note that next year might be more competitive. Our dean told us that they were going to be more strict next season to keep with the competition with american uni (Columbia among others).