Good afternoon Sakam,
Your friend may need to speak to an architect. The range is very wide depending on design, finishing, size, etc. To illustrate - I know 2 people who have built 1 bedroom units on 50 * 100 feet as follows:
1) 24 units for 24 million (very good finish)
2) 30 units for 20 million (okay finish)
The finish for high end units can cost as much as 50% of the cost of building.
What is your friend's budget, what kind of finish do they want, and for what kind of market (rental income)? Start with what you have, use a fair architect and see what can fit into the budget.
The other way to do it would be to decide the size of the entire development, and based on the finish, multiply the average cost (e.g. Kshs 20,000) by the area. So if you are doing lower middle class flats and the total area was 1000 square meters, then the cost@ 20,000 per sqm would be 20M.
When you live for others' opinions, you are dead.
- Carlos Slim Helu