hapa looks like cost ya nairobi and the environs, depending on the area and quality needed naona one can even reduce that cost, toa architect na engineer, reduce plumbing, toa landscaping, reduce those cabinets, na that approval ukiweza sort watu wa local government that can also reduce significantly.
Two identical structures can be built on opposite sides of the road,all other factors held constant the cost won't and will never be the same. Nyumba sio nguo ukipeleka materials unaendea two matching shirts.
Ni possible lakini quality of finishes will be low and you do not use a contractor, itakua unadeal na mafundi personally na ujue kile unafanya isikuwe mjengo yako ya kwanza. Haitakua na vitu kama tiles. The bathroom and toilet will be one for sharing in the house. Plaster and paint itakua ndani ya nyumba pekee. Fence itakua ma plants. I would say with 2.8 million bob you have a decent basic 3 bedroom bungalow ya kuondokea rent.
According to planning laws and regulations, all building plans must be approved and the plans are submitted by the architect. The authorities have the right to demolish any unapproved illegal structures within their jurisdiction. It is your kind of thinking that has turned our beautiful country into a shithole eyesore coz of the numerous unplanned and unapproved illegal structures.