CLASS vector functions

I am trying to access my functions of a class vector... without exposing my private variables.  I will narrow this down two functions that work together.  These functions worked fine, when they were pure class functions, but I need some help reworking them for the class vector.  I have tried to include enough code for you to attempt to run this on your compiler.

FYI... the code comes from 3 places (as per my professor's instructions).  I have included my search function (that is working) in case you see a need for it.
Any ideas?


#include <iostream>
#include <string>
#include <vector>
#include <fstream>
using namespace std;

THE CLASS:
#ifndef APARTMENT_H
#define APARTMENT_H
//Class for an Apartment:
class Apartment
{
public:
    Apartment(int buildNum, int aptNum, int BA_Num, int aptType, bool view, bool highFloor, bool rentalStatus, string cust_name, bool rent_paid);

    void newMonth( );
    double setPastDue (double rentDue);
    friend searchFor(vector<Apartment> &record);
    int the_BA_Num;            //building & apartment number combined

private:
    int the_buildNum;          //building number
    int the_aptNum;            //apartment number
    int the_aptType;           //apartment type (# of bedrooms)
    bool the_view;             //lake view (T or F)
    bool the_highFloor;        //high floor (T or F)
    bool the_rentalStatus;     //rental status (T or F)
    string the_cust_name;      //customer's name
    bool PastDue;              //past due status (T or F)
    bool the_rent_paid;        //rent paid status (T or F)
    double rentDue;            //amount of rent due
    double rent;               //amount of base rent
};                                      
#endif

THE FUNCTIONS:
    int search(vector<Apartment> record)
   {
        int BNum, ANum;
        cout << "What building number: ";
        cin >> BNum;
        cout << "What apartment number: ";
        cin >> ANum;
        int BA_temp = (BNum * 1000) + ANum;
   for (int i=0; i < SIZE; i++)
        {
     if(record[i].the_BA_Num == BA_temp)
           return i;
        }
        return SIZE;
    }


    void Apartment::newMonth( )
      //Precondition: Apartment object is set up.  Test for an outstanding balance.
      //Postcondition: Rent for new month is added to "rentDue".
      //      If there was an outstanding balance "PastDue" function was called.
    {
        for (int i = 0; i < SIZE; i++)
        {
        the_rent_paid = false;               //sets all rents to False
        if (rentDue >= 0.01)                 //checks for an outstanding balance
  //              setPastDue(record, rentDue);               //if so, calls "setPastDue" function
        rentDue = (rentDue + rent);        
     }
     }

    double Apartment::setPastDue(double rentDue)
      //Precondition: "newMonth" indicates that there is a dollar amount due.
      //Postcondition: Adds $50.00 to the "rentDue".
    {
        return (rentDue + 50.0);                     //adds $50.00 to "rentDue"
    }

THE FUNCTION CALL:
           //ADD ONE MONTH RENT TO ALL APARTMENTS
        {
        for (int i=0; i < SIZE; i++)
         {
         record[i].newMonth();
         }
         cout << "ALL RENTS HAVE BEEN UPDATED.\n" << endl;
                    }