can an agreement to repay a contract to repay a apartment complexs collecteion agency be recind by notice the same day.

An Agreement is binding in the State of Nevada upon execution of the written agreement and performance of the terms of the Agreement.  There are a number of ways to be able to rescind a Settlement Agreement (fraud in the inducement, etc.); however changing your mind is not a valid basis for rescission of an Agreement.  Therefore the better course of action would be for you to examine one of two arguments: (1) the Collection Agency breached the Agreement; or (2) the Agreement is void/voidable due to improprieties by the Collection Agency in inducing you to execute the Agreement. What complicates matters is that your question indicates that you are not merely looking to set aside a contractual agreement but an actual stipulated judgment.  Setting aside a Judgment is more complicated in accordance with Nevada Rule of Civil Procedure (NRCP) 60.  If the Court has already entered a Judgment, then you must file a Motion with the Court under NRCP 60(b), and timeliness is key to your motion.  The Court can set aside a Judgment within the six months of entry of the judgment "upon such terms as are just" for (1) mistake, inadvertence, surprise, or excusable neglect; (2) newly discovered evidence which by due diligence could not have been discovered in time to move for a new trial (not applicable in your case); (3) fraud, misconduct or  misrepresentation of the other party.  You can file a Motion alleging a Judgment is void at any time; however that it is likely not applicable to you.  You can likewise file a new/independent lawsuit against the Collection Agency to relieve you of the Judgment or claiming a fraud on the Court; however such steps would likely not be your most effective course of action.