New Jersey, like the majority of states, does not allow the waiver of lien rights prior to work. N.J.S.A § 2A: 44A-38 specifically notes that:

“Waivers of construction lien rights are against public policy, unlawful, and void, unless given in consideration for payment for the work, services, materials or equipment provided or to be provided, and such waivers shall be effective only upon and to the extent that such payment is actually received.”

So, in all likelihood, such a clause would not be enforceable if contained in the contract, and shouldn’t be included in the first place.