How much more should I charge for the bigger master bedroom with private bathroom?

Depends on how extensive the remodel work is, a cosmetic flip paint, trim, cabinets, vanities don't trigger permits here in WA state. 

To ensure your STR performs well, do your kitchen and bathrooms need to be fully renovated and updated?

The property consists of ten 1-bedroom, 1-bathroom units, and two 2-bedroom, 1-bathroom units.

Leave atleast two rolls per bathroom. 

For instance, a three-bedroom, one-bathroom property listed at $1,450 has been available for 37 days (zip code 43205) or a two-bed, two-bathroom property listed at $1,900.

The seller said the house has three bedrooms two bathrooms and a den, but he does not know the square footage.

It includes a 3-bedroom, 1-bathroom ranch house along with a private street hosting a small mobile home park with 5 units. 

Try looking into zillow/Redfin and see what your potential rents you can get near the neighborhood by filtering the bedrooms/bathrooms of the intentional property that you are planning to buy.

We have an 11-unit apartment building (five 1br/1ba, six 2br/1ba) and want to do a cosmetic rehab (new kitchen, bathroom, paint, sanding, and staining hardwood floors, excluding repairs on MEPs).