Talk to a lawyer. Do not make legally binding decisions based on advice you get from the internet. But as the other commenters have noted (including the dead

Talk to a lawyer. Do not make legally binding decisions based on advice you get from the internet. But as the other commenters have noted (including the dead guy): do not sign an NDA to talk with an investor. NDAs should not be part of the investment relationship. If they are, the fundamental trust necessary for a working relationship is absent and nothing good will come of it.