Several questions about getting a master degree in mathematics in US Currently I am a junior at UCLA. I have taken some math classes and they seem really interesting. However, I am not sure whether I should pursue a PhD in mathematics. So instead I'm thinking about getting a master degree. However there's very few information about master in mathematics online. 

Question 1: How rare is it for people to go to industry first and then go back to academia (after 2 years, for example)? How should they deal with the recommendation letter part?

Question 2: Some of my friends have been taking honour classes since they were freshman. However I used to be a math/economics major so I've been taking regular courses. How would that impact my application? (suppose I'm NOT talking about master in computational finance or financial engineering. I took a class in option pricing and interest rate model, worst "math" class ever)

Question 3: Is there any "rule of thumb" of determining whether someone should pursue an advanced degree (master and PhD) in mathematics? I remember once one of my TA told me that "if you cannot get six A's, then probably this is not the right path for you". Now, my major GPA is 3.8. Got 3 A's in upper (analysis and linear algebra), bunch of A- (complex analysis, differential geometry, probability), and B+ for abstrac algebra. 

Any advice/insight is greatly appreciated. Thank you very much.
Q1. Not rare at all; especially for Masters programs. They probably deal with it as everyone else: contact a professor that they did well in their class and that class relates to what they want to study afterwards and ask politely for a reference letter. There are some cases (eg. you are more than 5-6 years after your graduation) that you may not need an academic reference but these are edge cases and do not apply to your case.

Q2. Depends what you want to study. If you are thinking of doing something with conjunction with Mathematical Finance or Econometrics/Economics this might be viewed as a positive thing. For Ring Theory? Probably not so positive. 

EDIT (based on your edit) As you clarify now you are not thinking of something associated with Finance and/or Applied Maths generally.  If that is the case, most probably not having honours class will be detrimental. Having said that, if you apply for MSc it should not have a significant impact. After all you are apply for a MSc so you can do classes like that.

Q3. The only rule of thumb I can think of about pursing a PhD is liking your subject a lot. And even that is a rule of thumb. Sorry to say but your friend's advice about "six A's requirement" etc. is ungrounded advice. Sure enough if you are not good at something you should not have illusions of grandeur either though. :) 

EDIT (based on the comments) 
According to the interesting discussion in the comments: Take into account that you risk not having a house mortgage at 27 as well as one day waking up and realizing nobody will pay you to do Approximation Theory. (Actually, I think you should consider this as extremely likely. Don't worry though, even if this happens chances are you 'll survive it.)