Quick question, as my search-fu fails me. I know that if you need 5 ranks to qualify for a prestige class you can be in there at level 6 at the earliest, but can't find the source to back this up. Anyone have a quick link?
well you need to meet the qualifications before you can take the class. at lv4 going into lv5 you don't yet have 5 ranks in a skill and you can't use yourself to qualify for yourself.
It comes down to order of operations. When leveling up you choose the class to gain a level in first and then apply skill ranks based on the number allotted by that class. Thus, yes... you need to be at least character level 6 to qualify for a prestige class requiring 5 ranks in a skill.