Initially to two-time had a meaning as a term for being unfaithful to a spouse or lover. Secondary derivation of the term was to deceive; double-cross.
It recently developed into a fashion/social situation where individuals lead two separate lives, one as corporate slaves, office employees or clerks and other as artists of any possible orientation.
The term first started developing in Hollywood, where many wannabee actors are forced to have other jobs while waiting to be discovered by big studios and made famous and has since infiltrated various fields of art and everyday life.
This phenomenon is well illustrated in Will Self's short story "Short history of english contemporary novel"
like an episode of Candid Camera-- a publisher whines to a writer over lunch that there are no writers left in England writing novels, and is predictably inundated with zany scripts from the next five people he meets....who are all working as waiters or maitre'ds.
Symptoms that will allow you to recognise a two-timer include edgy, tense behaviour coming form lack of sleep, bags under eyes, heavy caffeine addiction and
over protective behaviour regarding minute points of her /his artistic/creative work as opposed to the financial slavery.