I think it really depends on what stage you r in your life. If you are still in school, maybe $0 is not unreasonable. If you just started working, 2-5k is not a bad amount already.
While that's the most common recommendation that is being touted all over the place, what is the rationale behind it though? Depending on your line of work, 3 months may or may not be enough to get b ...
力哥﹐我估 rationale 係萬一出咩事 (例如車禍)﹐你需要大概3個月的 NET INCOME 來生活掛。。。