Calculating cost basis on rental AND ADU

Ok here's the situation: 

 

I have a property that has a main house and a carriage house (ADU). I have rented the carriage house since 2018, and I believe that I calculated the cost basis properly to capture depreciation in 2018.  I used to live in the main house.

 

Now I rent BOTH houses.

 

Do I now calculate cost basis separately?

Is the cost basis for the main house my purchase price minus land? 

How do I enter this into turbo tax?

 

Thanks for any help in advance.