It'll drain fine with 1 1/2" as long as you're not doing jets or anything high volume.

Obviously homebound is not a real plumber

The answer is, whether it will drain or not doesn't matter, A tenant is not legally permitted to alter any attached real property within the structure.

I figured he/she was using the term loosely, as in unit, condo, flat, etc.

Emaemes, are you actually renting? Please clarify for us.

It's an apartment on the 3rd floor.....It's a condo...I purchased it....
Unusal building....90 units, 37 layouts, so apartment don't line up, as you would usually expect....
The town code requires a 1 1/2" drain for a tub, and a 2"
drain for a stall shower...My intention was to put a stall shower in place of bathtub....but don't want to dig up floor , and go to enormous expense...Building probably wouldn't allow, if I wanted to....

Code requires the 2" drain, and if you don't want to remove the floor covering to alter the existing drain, then you will not be able to do what you want. It's not that big of a deal to chip up a bit of gypcrete. It's much softer than actual concrete. However, in a multi family dwelling, only a licensed plumber will be allowed to modify the building systems. No DIY allowed. Call some plumbers and get some estimates. Other occupants are sure to have done the same thing.

Concrete under tub.....no can do....
We're trying to get the building plans, to see if they put 2" drains under all tubs and showers....
There are many tubs as well as stall showers in the building.....

I doubt seriously if there is any gypecrete in that building. More likely it is a 3 or 4" concrete slab on top of a steel pan supported by steel trusses and the visible ceiling on each floor is a drop ceiling below the trusses. All utilities are in the truss space so they could change it to a 2" drain, but it would entail displacing the ppl in the dwelling unit below while they open up the drop ceiling, all in all, I think the whole project would prove to be cost prohibitive.

I probably prefer a dedicated shower too, but if that's the only bath in the place, big mistake for resale. Even if it's an apartment, people expect at least one bath.

Code requires a minimum of one bathtub

There is a bathtub in the 2nd bathroom......For some reason, which I don't understand...both bathrooms have tubs..no stall shower in unit.....Strange building....No two apts. line up.....Many different layouts.....Many apts. in building have both a stall shower and tub in master.....Some have a tub in master and a stall shower in 2nd bath....It's very strange....I'm thinking that it must have to do with the plumbing..Building was completed in 2009, but all units were not built at the same time...Mine is one that was just completed, so I will be the first to live in it....