I think the title should have been 'Impacts of NPHP on Pakistan/Pakistani Realestate'
Anyways,
1 Assumptions:
A. 5 million New Houses (literally a new Pakistan)
B. 5 Years
C. 5000000 x 6.8 = 34 million people get a roof on them
(avg. household size is 6.8 people/house in Pakistan [REF-1])
D. New/Existing = 5000000/19211738 = 26% increase of housing units to the existing inventory [REF-2]
2. Data & Facts:
A. Pakistan spends USD 5.2 billion on construction/ year
B. 2% of total GDP [REF-3]
C. USD X for land purchase (X because land cost has high variability compared to construction)
3. Implications on Society & Economy
Keeping all the assumptions in place that can be a historical revolution with 26% growth of units in just 5 years & 34 million people get a roof. Minimal USD 26 billion circulates in economy and minimum 2% of GDP secured for 5 years (Employment growth is a massive added benefit)
4. Ground Reality
However, politics cant be kept aside, at the end of the day this project's foundations are socio-political (Society & Politics is in the DNA of this project). The figure suggest that in next 20 years we can have more houses than we had in past 71 years.
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5. The Emergence & Growth of the Mortgaging Model in Pakistan
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To me, with all the assumptions and facts, most interesting part seem to be Government level initiative to invite the banking sector into the construction/housing model of business. There is house mortgage in Pakistan but almost like a dead-horse and never flourished as the Auto Financing in Pakistan.
As per my view, I am highly skeptical of the 5 million figure, however, even if 0.5 million units get materialized, as planned by the Government to introduce a refined house mortgaging model, considering the citizen's ease and comfort it will be a massive initiative. Why pay the landlord for your life time when you can pay the government/bank for approx 20 years to get a home for your family.
6. Religious perspective of Mortgaging in the context of Riba (interest/soud by banks)
I am no expert at all, I may be absolutely wrong but as per my little knowledge (referring to some scholars/domain experts) this does not qualify as being Riba or interest filled based on Usable vs Consumable product [REF-4] [REF-5]. I am happy to stand corrected on that.
7. Conclusion
To me, 5 million sounds good for our country & its impact on housing, society, economy etc. but much more interesting and dynamic would be to see how the project will be executed. Currently mortgaging is a highly neglected factor in Pakistan. Malik Riaz has bought a bank [REF-6] so he may be on the path of Mortgage-driven housing more aggressively, in nearer future. Customer buy from Bank and Bank buy from BT. In today's world and life the middle men are the mega winners in any transaction related activities (Careem/Uber, Amazon, Air BnB etc.)
Your second question:
"Also, second thing .... how much percentage?"
Sir no one knows (its not even an assumption, its a non-existent hypothesis, unless the exact or approximate locations for the project have been marked)
[REF-1] Pakistan Average Household Size https://www.arcgis.com/home/item.html?id=8aead66ab8894fa49dbf3f92e1adbfc3
[REF-2] Total Housing Units in Pakistan http://www.pbs.gov.pk/sites/default/files//tables/HOUSING%20UNITS%20BY%20NUMBER%20OF%20ROOMS%20AND%20TYPE.pdf
[REF-3] Real estate in Pakistan
https://en.wikipedia.org/wiki/Real_estate_in_Pakistan
[REF-4] Are Mortgages Islamically Permissible? | Shaykh Atabek Shukurov
https://www.youtube.com/watch?v=wtY-CeSHkSI&t=545s
[REF-5] Is taking loan and mortgage Haram | Javed Ahmad Ghamidi
https://www.youtube.com/watch?v=STawmMVP1L8
[REF-6] Bahria Town to acquire investment bank
https://www.dawn.com/news/1313321