Sri Lanka - Small 01 Bedroom Single Floor House in Sub-Urban Colombo

I am 55 Years Old Professional who lives in abroad. I inherited a 50 Perches Land in suburban Colombo.

I would like to know the approximate cost of building a Single Floor, Single Bedroom Small House (somewhat similar to One Bedroom Apartment) with following criteria:

1. Total House (inside) would be around approximately 790 Sq. Ft. (28' x 28')
2. The Roof of the house must be 15 ft from the inside (floor) of the house floor - (at the lowest Height - at the outer wall of the house).
3. Should have Doors (Three) with 8Ft Height and should have Seven (07) Windows (7' x 7')
4  There are should be a 6 Ft Corridor around the house; The roof must cover this area as well. The Height of the Roof at the Edge Corridors must be at 10 Ft - This means additional of 816 Sq Ft Corridor area around the house.
5. The House floor and the corridor must be 2 Ft above the land level
6. The Bathroom must be of 8' x 8' Size
7. The House must be positioned in one of the rear corners of the square land (50 Perches); A Bus Route in the front.
8. Therefore, the total area of the house would be 790 Sq Ft Inside and 820 Sq Ft Outside Corridor
8. The Septic System is required and it should be in the front area of the land

Though the concept may look bad and waste in a large corridor area, I would like to know the approximate cost to build the above house (Value in SqFt or in an approximate calculation).
(Due to certain physical difficulties, storeyed house is not considered).