3 tenants on month to month agreement lease

[Leticia Vasquez-Lehr]

3 tenants on month to month lease 2 a couple and single Mom. Single Mom decided to leave within the first without given 30 day notice. She put half of the deposit and now wants that back. Original rental agreement was $1600 deposit. 1) Do you return the deposit? If so, how much? Also, is the couple that remains in the premises responsible to complete the rest of the deposit? Thanks!