Oh wow! Thank you for all the informative responses!
To clarify a few things.
1) I will either be based in Philadelphia or NYC. (If I'm in NYC then I'm not sure which airport to be based out of, I can choose either).
2) When I said random places, I'm referring to Bloomington, Indiana or Nebraska. Hahahah, didn't mean to offend any international members

sorry!
3) I'll be rotating client location every 6 months, but in general most of the clients are in the east coast of the US, if that helps.
4) I wish I had frequent international assignments hahaha. I might have 1 or 2 in the next few years but nothing drastic enough to consider it a factor.
Any additional info is well received. From these responses alone I'll be able to run searches within this forum for more detailed information.
QUICK RANDOM QUESTION: Can I give my miles to someone else so they can have free flights? Like, let's say I want to give my parents a free vacation

do all airlines universally allow that, or are there certain airlines that are easier to do those things?