Earlier quoted context omitted.
This is common across the developing world. Not a lot of people out of our close to 8 billion can afford such a huge expense in one go.
Even in the US this is the case. Government regulation has outlawed people building incrementally in most cases, so people who can't afford to buy a house generally have to rent forever. Building a house is usually more expensive than buying a similar house, due to building codes, permitting costs, and costs of utility build-out.
If you find a house for sale built by the general contractor for themselves, it's probably very well built. In a lot of ways that wouldn't be obvious to the vast majority of people.