How far can one go with 1.5m in building an 8-room self-contain in a suburb of Abuja , got a plot of land already.

No!
Let me scale it down for you in stages.
STAGE 1 FROM FOUNDATION TO ROOF SITTING.
u gonna need wroghly 6000pcs of block; amounts around 600k, around 200bags of cement multiply by how much they are selling is in u area close to 400k, nothing less than 200- 250tons of sharp sand around #200k, 100tone of granite @ #250k for concrete blinding, German's floor and lintel, 60lenghts of 12mm Iron rod, quarter rods, biding wire, 1by12 planks, 2bags of 3" nail for lintel @ #200k, book #50k for water 500k for workmanship. Total around 2.5million
That is from foundation to roof sitting, but I will advice you to first build two or 3, then use it as collateral to get loan and then use it to develop the rest.

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Thanks gr8david for your detailed response.

If I were to take on 3 rooms first how far will 1.5m go?

I noticed you did not go ahead to talk about d roofing and firings (internal) probably because by your calculation the 1.5m is already exhausted. I do not want to engage and get stock halfway.

1.5million will complete roofing, plastering/cement flooring n ceiling, but wiring, tieling, toilet/kitchen fittings I can't guarantee.

Nice one gr8david, I think your idea to take on 3 then use as collateral for loan might be the best option. Thanks.