Financial affordability

Can you please advise what would be the budget of a normal employed income family to purchase a house in islamabad, lahore, karachi, hyderabad, multan, faisalabad ?? How much can they pay as a down payment and how much can they pay per month to pay off the balance ?? I am looking at building affordable homes for lower middle class people who do not have a home of their own and cannot come up with a lot of cash.