The biggest challenge is genarally poo-pooed, but it is serious. It will be your inability to speak Hebrew perfectly. No matter how well you think you will be able to speak Hebrew like a sabra, you probably wont be able to and this will impair your ability to get a good job as good jobs requires a mastery of Hebrew immigrants just cannot get.
No matter how much you think you can read hebrew or Ulpan you will never be good enough to get a good job. The best jobs in Tel Aviv and Heriliyah require a level of hebrew only a native born can get. And apartments in Israel are expensive, if you think they are expensive in Brooklyn or Monsey, they are exactly more expensive in Jerusalem and you make less money