The most economical way to go about it with kes 1m budget is through pooling resources as is being discussed here.
www.a4architect.com/discus/topic/joint-investment/This way, you will own a 20m2 bedsitter with chances of increasing other rental units vertically in future.
For this, you will have to team up with other like minded Kenyans and execute the project with ownership under sectional title or LLC.
With this, there is a guaranteed 10% ROI.
The next best option is Sucasa.
Sucasas 18m2 costs 1.3m and has no option of future expansion.
The other option is to buy land in the middle of nowhere for 0.5m and build a mabati shack for 0.5m. Here, you cant use the house since its too far from tarmac eg Jamii Bora situation.
As Iron Sharpens Iron, So one Man Sharpens Another.