Getting "null" in my output

import javax.swing.*;

public class Rental {
  public static void main(String[] args) {
    process();
  }//end main method
  public static void process(){
    String output = "";
    String input = "";

    int count = 0;

    input = JOptionPane.showInputDialog("Enter the number of houses that will be looked at: ");
    count = Integer.parseInt(input);    

    String[] address = new String[count];
    String[] city = new String[count];
    String[] state = new String[count];
    String[] property = new String[count];

    int[] zip = new int[count];
    int[] location = new int[count];

    double[] inspectionCost = new double[count]; 
    double[] repairCost = new double[count];
    double[] totalCost = new double[count];

    double totalExpense = 0;

    int waterfront = 0;
    int nonWaterfront = 0;

    for(int i = 0; count > i; i++){  
      address[i] = JOptionPane.showInputDialog("Enter the street address: ");

      city[i] = JOptionPane.showInputDialog("Enter the city: ");

      state[i] = JOptionPane.showInputDialog("Enter the state: ");

      input = JOptionPane.showInputDialog("Enter the zip code: ");  zip[i] = Integer.parseInt(input);

      input = JOptionPane.showInputDialog("Enter the cost of the inspection fee: \nWaterfront: 1 \nOther: 2");  location[i] = Integer.parseInt(input);

      switch(location[i]){
        case 1: inspectionCost[i] = 100; waterfront++; break;
        case 2: inspectionCost[i] = 50; nonWaterfront++; break;
      }//end switch statement

      input = JOptionPane.showInputDialog("Enter the cost of repairs for the property: ");  repairCost[i] = Double.parseDouble(input);
      
      totalCost[i] = inspectionCost[i] + repairCost[i];

      property[i] += address[i] + "\n" + city[i] + ", " + state[i] + " " + zip[i]  + "\nTotal Cost of Rental Property: " + totalCost[i] + "\n\n";
      
      output += property[i];

      totalExpense += totalCost[i];

    }//end for loop

    output += "Total expected from all owners " + totalExpense + "\nNumber of waterfront rentals: " + waterfront + "\nNumber of non-waterfront rentals: " + nonWaterfront;

    JOptionPane.showMessageDialog(null, output);

  }//end process method
}//end Rental Class