By the way, one of the biggest myths of bass playing is "you need an extended range bass to play along with piano/organ/keyboard music, because of all the low C's and D's."
However, bass is a "transposing instrument" that sounds 1 octave lower than written. So when you are reading sheet music for keyboard, you should play it 1 octave higher than if you were reading sheet music written for bass.
Piano "low C" (2 ledger lines below the staff) is at the 3rd fret of your A string (or the 8th fret of your E string) and does not require a 5 string, contrary to popular belief.
However, bass is a "transposing instrument" that sounds 1 octave lower than written. So when you are reading sheet music for keyboard, you should play it 1 octave higher than if you were reading sheet music written for bass.
Piano "low C" (2 ledger lines below the staff) is at the 3rd fret of your A string (or the 8th fret of your E string) and does not require a 5 string, contrary to popular belief.