I was told if I join the military, that I will be a E-2 right away due to having prior college credit.?

If you enter in an advanced rank due to college credit you will be paid as an E-2, but you won't officially be called as that rank until you graduate basic.

Others who get advanced rank due to 6 year contracts and other things get paid as their advanced rank after basic.

I don't know which branch you are referring to since they all have different promotion speeds to get into detail.

Most everyone who isn't advanced because of college credits or any other reason is still an E-1 after leaving boot camp and in most cases reporting to their first command.

Then the rotation for E-1 to E-2 is 9 months, the rotation from E-2 to E-3 is 9 months then the wait time to take the E-4 exam is 6 months.

(This is all for the navy side of the house, but I imagine the first part of that is about the same for each branch)

If you have completed 24 credit ours or more you will enlist as an E-2 and be promoted before you go to basic training. For the Army at least.

AR 601-210 2-18a(6)

Has successfully completed 24 or more classroom semester hours (36 or more quarter hours) at an accredited degree granting college or university list in the AIPE or NACES (foreign transcripts must be evaluated according to para 2–7f and 2–20) may enlist at any time at pay grade PV2.

AR 601-210 2-18a(7)

Has successfully completed 48 or more classroom semester hours (72 or more quarter hours) (without a 4-year degree) at an accredited degree granting college or university listed in the AIPE (foreign transcripts must be evaluated according to para 2–7f and 2–20) may enlist at any time at pay grade PFC. Applicants with an associate degree will be enlisted at pay grade PFC without regard to the number of semester or quarter hours completed.

you will be paid as an E2 from day one. you will not put the stripes on until after you get out of basic.

you must serve a minimum time in service before you can be advanced to E3. Think it is six months. might be 9.

It depends on your branch. They are not all the same.

It will be after bootcamp. Everyone in bootcamp is an E1. Those who earned a promotion, will be an E2 or E3 after bootcamp. You will be an E2 after boot camp.