After coming to US on a K1 Visa and marrying a US citizen;

1) How long should I wait before applying for naturalization after marrying a US citizen? (marriage after entering on a K1)

2) How long time should I expect to wait before I could submit I-130 for my parents and my unmarried brother (under 21)?

2b) How long does it take to get through the entire process, till they actually can move to US?

3) If my unmarried brother decide to study in US before we do the I-130; can we apply for the I-130 while he is on a F1 status?