This is a rule I wanted to make sure about, I read somewhere that if you have a class with a certain skill on it, you can rank that up normally. However if you later go into a class that doesn't have it, the max ranks are the same but it costs 2 points for 1 rank unless you have something like able learner. Is this true and if so was there any errata to it?
Yes, this is all correct. No, it was never errata-ed. From the SRD:
Regardless of whether a skill is purchased as a class skill or a cross-class skill, if it is a class skill for any of your classes, your maximum rank equals your total character level + 3.
So if you take a class which has Appraise as a class skill, the maximum number of skill points you can put in Appraise will always be your character level + 3, regardless of what classes you multiclass into.
Each skill point you spend on a class skill gets you 1 rank in that skill. Class skills are the skills found on your character’s class skill list. Each skill point you spend on a cross-class skill gets your character ½ rank in that skill. Cross-class skills are skills not found on your character’s class skill list.
If you level as a class, each skill point you spend on a class skill gets you 1 rank, and each skill point you spend on a cross-class skill gets you a ½ rank. As you say, Able Learner changes this, but without it, cross-class skills require 2 skill points for each rank.