Nurse Manager

I am new to the role of nurse manager in a small (6 full time and part time employees) I am struggling with staffing. this system of staffing was broken when I started 3 months ago. The NM before me didn't care or do much except cover ALL the shifts that needed covered when staff were off on vacations. That is why I presume I walked into a mess. She spent so much time covering for them, she didn't get any of her work done and therefore the staff have come to expect that I do the same. I am beyond frustrated that it is expected of me to cover every shift they can't find coverage for. I work a 40 hour week and am then expected to cover their weekends so they can be off having fun!!! Seems unfair to me. I don't mind helping out with call-ins etc, and have worked several night shifts, a lot of times after working an 8 hour day and it is exhausting. I get behind on MY duties as the NM. This is how scheduling is right now. Guess I should say I am the NM for and IL/AL nursing team with HHA as well. I have one LPN that works strictly Sun,. Mon, Tues days and one that does the same schedule on nights. I have one LPN who works Wed, thurs, fri days. One LPN that works wed nights only. One LPN that works Thurs, Friday and EO Saturday. I then have 2 at times 3 prn staff that will fill in the weekends/help cover. These nurses have gotten to pretty much run how they want things done and I can see my program failing, residents families have already come to me several times with complaints. I keep getting told, "we don't have the money to hire more staff" I am frustrated. How do you all do your staff scheduling....I am open to help and ideas. Please be kind, I need support...