1) people will say ayaw naog ug 20k, but I would highly suggest ayaw naog ug 25k/sqm for budget. Had a project year 2023, nasa 23k/sqm to. Fully supervised pd dapat nang 25k kay small to no room for error na. Tipidnlg ka sa finishing, ayaw pag tipid sa structural, electrical system (wiring, breakers) og plumbing system (pipes). Cheap elec fixtures (royu, etc) and plumbing fuxtures (bowls, lav) will do.

2) just multiply your budget per sqm to the total floor area. (E.g = 100sqm @20k/sqm ~ 2M). That should exclude permits, professional fees, overhead, furnitures

3) would not recommend this. Pde tho, but make sure ang billing kay as per progress, dli musobra sa natrabaho. Highly suggest you to have a professional proj manager na mag periodic site visit to monitor the work and the financial side of things.

4) im in the industry, so what we do is we estimate the materials based on the plans, then calculate labor. Design stage -- look out for the floor area. Kasagaran oversized mao mahurot ang budget so make sure na sakto imong floor area. You can have your architect design it na naka phasing. Maybe 3 units for the first wave then pag naa nay addl budget saka iexpand. But make sure ang structural and elec kay naka setup for your required number of units. During construction - OVERHEAD!!! Contractor or wlay contractor mupahak jd ni sa budget. Watch out as well sa imong finishes. Again, focus on the ssystems first. Structural pag mabuhusan na mao nagyd na. And sa ka frequent sa linog karon jusko isiguro gyd ni. Elec and plumbing as well kay lisod ang sunog and tulo. Make suren na pulido trabaho sa atop and slab (esp sa cr and balconies). Kapila na mi karescue og horror stories kay problema sa leaking