one at home for sure for four weeks--some programs request a LOR from the PD at your school. honestly, you probably have to do only one other away. two is probably average, but one 4 week would probably suffice. there are two reasons to pick a particular program to rotate at 1) because you want to get a letter 2) you might want to go there.
timing depends if you need to do well on step II. if you can push it back to at least oct, then i would do your two-three rotations as soon as possible. early helps get your letters on time, its easier to get spots at places you want to go, and youre done early (so youve got that going for you. which is nice)... the downside, you porbably wont be that well remembered come february. letters have to be in before early or mid november at most places... you should give at least 2-3 weeks time for them to get done... often it takes writers longer... so getting a letter from someone you met in october would be very tough. consider doing your home one during your third year... that would help save time later. three ortho months back-to-back is pretty exhausting. the last thing you want, is to look tired or stupid. thats why i think doing three or less is a better idea. not to mention, its expensive. id estimate at least 500$ more into your budget per away.
hope that helps.
