Most brownstones aren't big enough to have a full-time super. There are lots of different possible layouts. Sometimes the basement apartment has full access to the back yard; sometimes there are stairs from the 1st floor to the garden, sometimes the basement and 1st floor are a single-unit duplex, sometimes there is single occupant in the whole brownstone.
When I lived in a brownstone in Cobble Hill (Brooklyn), even though we had three floors and five bedrooms for four people, we still did not have access to the garden because the basement apt did.
For garbage, we had a gated area out front next to the stoop that led to the basement front door where the garbage bins were stored, and then we brought them to the curb every week.
Note 1: Everyone marked their bins with the house address because otherwise people would take them.
Note 2: Regardless of what it was, whatever you left on the curb at any time of day would be gone within 10 minutes.