It is possible to live in Manhattan for $70K/year--with roommates. However you should not have any financial shocks. You should not, just to name a personal example, find yourself suddenly needing three dental implants at $2700 each, not including the cost or surgery. You should avoid cabs and use public transportation instead. And you should avoid taking advantage of any cultural activity that isn't free.

One downside of taking lower paying jobs is that employers often decide that you really are worth the lower salary. Programmers can end up doing system administration and desktop work. Perhaps that's not too bad in moderation, but it's very easy to get sucked into an on-call mode. Then again there may be exceptional people who can program in their heads as if they had an office with a door they can close, while some administrative assistant is nagging about corrupted email.