Minor Chords
Many of my students have been confused by the difference between "flat" and minor. I'll try to clarify the matter.
Flat refers to one pitch. The black key next to the C on a piano is a Db (D flat). It can also be called C# (C Sharp). But it is not a D minor, nor is it a C major.
You can not have a minor note. Minor requires an interval. A relationship between more than one pitch. You can have a minor third. You can have a minor chord. You can have a minor scale. But there is not a minor note.
So a Bb chord, is a major chord built on a Bb root. A Bm is a minor chord built on a B root.
If you are looking for an A#m, use the Bbm
If you are looking for a Dbm, use the C#m
The following chord can be Ebm or D#m.
In the key of Db, it is Ebm, the ii chord.
In the key of B, it is D#m, the iii chord.
If you are looking for an Abm, use the G#m
Here are some excellent books on the subject