Instead of debates and personal opinion, look for proof https://www.ladbs.org/docs/default-source/forms/plan-check-2017/single-family-dwelling-duplex-plan-review-list.pdf under G (Interior Env) which defines the minimum requirement of a habitable room (aka bedroom or bathroom).

Everyone has their own room and a bathroom and they share common space such as living room, dining room and a kitchen and they are one the same lease.

They have already called a real estate agent to list on the MLS and when the agent comes over to take the listing, they tell the prospective seller that the dog poop in the living room has got to go.The rot in the bathroom behind the toilet needs to be fixed.

It costs the same thing to fix a hot water heater or remodel a bathroom on a $200K house as a $100K house.   

The bathroom was gutted 2 years ago and the kitchen will be soon, some walls/ceiling are in good shape, but aside from that some walls need more than just paint.

14 - How many bathrooms will there be?

houston is probably similar pricing to Columbus Ohio but way worse zoning laws. we take 20% on top as a GC and a guaranteed fee agreement. our contracted new construction projects recently:Single family new build spec home: 1513 square feet with 3 beds 2.5 baths 1 car attached $275000 approx $182 a square foot if calculated using heated square feet which means our cost is $145 a square foot. 3 unit / triplex new construction: 2008 square feet 2 bedrooms 1 bath per unit or total 6 bedrooms 3 bathrooms with 3 off street parking spaces. contracted build cost $395,000. no garage on this and better economies of scale with shared roof, slab, etc. $192 a square foot hard cost with our cost running approximately $157 a square foot. 

So your additional ~240 SF could be the foyer, hallway and bathroom spaces that are allocated by percentage to the unit.

Bathrooms: Especially the primary bathroom!

After repair value is $100k-$170k (based on comps in the neighborhood, the range is large since the layout is a bit weird where the primary bathroom is in a bedroom).