My 1888 build was lifted at some point in it's life, limestone foundation was replaced by poured concrete/block.

Although Philadelphia offers detailed zoning and use requirements, I am struggling to find concrete information on the requirements for certain bonuses.

I have some that are newer, but they were poorly insulated in the floors so a downstairs tenant can hear the upstairs tenant close their refrigerator, have a phone conversation, or make babies.

The quick math tells you you have 6000 ft per floor so 60x100 works for 18 units and 8000 ft per floor for 24 units or 80x100 so your actual dimension will depend on site constraints.

The other project was repairing the wood floors where an old in floor heater used to be and then refinishing the homes wood floors.

Painted interior, laminate floors, stainless steel appliances, and replaced all windows with premium energy star windows(did this more because the windows all were past due).What was the outcome?

Tenant's dirty clothes are all over the floor, people got to step over it, smelly dishes in the sink for weeks, and people had to hold their noses to see the place in addition to seeing my filthy tenant with his foot long beard.

If you're not on the water or AE zone, then rules for ADUs / living space on first floor of home are not as strict ; I learned the hard way ; Definitely need a contractor who will get the required permits for you.

I’ve been to India and yes the concrete construction most the world uses is much different than the US who benefits from all the Canadian lumber etc.

Shower tile, floor tile, splash, cabinets, paint we did ourselves while the laminate flooring, ceiling re texture, counter install were hired out.