Something like this should work.  This is assuming that your radio button has a class name of "myRadioButton" (lines 5 and 12) and the value for the delay 30 days option on the radio button is "Delay" (line 12).

$(document).ready(function () {
    
  //Run the function when the form is loaded and when the radio button changes.
  SetDateMinimum();
  $('.myRadioButton').change(SetDateMinimum);
  
  //Function that updates the minimum date on the date field.
  function SetDateMinimum() {
    var todaysDate = new Date(); // Gets today's date
    
    //If the radio button is set to a value of Delay, add 30 days to the date.
    if ($('.myRadioButton input:checked').val() == 'Delay') {
      todaysDate.setDate(todaysDate.getDate() + 30);
    }
    
    // Min date attribute is in "YYYY-MM-DD".  Need to format today's date accordingly
    
    var year = todaysDate.getFullYear();                        // YYYY
    var month = ("0" + (todaysDate.getMonth() + 1)).slice(-2);  // MM
    var day = ("0" + todaysDate.getDate()).slice(-2);           // DD
    
    var minDate = (year +"-"+ month +"-"+ day); // Results in "YYYY-MM-DD" for today's date 
    
    // Now to set the min date value for the calendar to be today's date
    $('.PropDate input').attr('min',minDate);
  }
 
});