I live in these apartments with help of a program. They pay a certain percentage of my rent and every three months the rent raises. This guy downstairs use to work with my sister a while ago, he always asked her out to dinner, he is a married man. I live upstairs from him and every since he seen my sister around here only drama is around. He comes up to my sister screaming and just being really rude like slamming the door in her face, calling her out of her name. The wife of the guy came up stairs screaming at my sister and my sister told her the whole situation. The wife said she was sorry and that she was going to leave her husband. I didn't know who my sister was talking about until about 2 weeks ago. This problem has been for about 1 month in half. Well about 2 weeks ago he came up to me screaming at me in my face saying that we have to stay away from his family and he is going to get his daughter to fight me and that I have one more chance or else something is going to happen to me... so I went to the manager and tried to solve the problem before it got worse, they told me that since my sister doesn't live here then they can't do anything and she just can't be around, my sister is homeless with newborn twins and a 2yr old. I am letting her stay here until her sec8 comes in. The manager said that she would tell to stay away and I will stay away. Well that was last week and today the wife and her daughters came up to my sister and was calling her a BITC* and was acting like they were going to do something. Now my sister wants to fight them. But I don't know what to do. IF they fight then I get kicked out of my house and I don't have no place to live. But if I tell my sister not to fight then I look like a bad sister that is not by her sister side when she needs me. I know this whole problem is the mans fault but now I am scared that he will come upstairs and try something when my son is here, I don't know how to handle this please help me...

Call the cops and get them involved.
Nobody should be harassed at there place of residence.
Your sister needs to walk away from the situation.
If you do call the cops and the neighbors do something then you have grounds for a restraining order.

The manager said they have the right away because they have been living here for years without any complaint, and if this persist they will have to let me go but I asked a lot of people and all say they have had a problem with him but I don't think people have brought it up with the manager cause they were probably scared. I have only been here 4 months. Should I do that now or wait till they say something else or wait till the manager gets involved?

Do something now, before it gets worse.

Definitely no fighting... and definitely report what is going on to the police - with special emphasis on the safety of you and your child. Be open and honest with the police and ask for help in dealing with these threats. If they cannot do anything directly, they may be able to refer you to another social service agency that can.

I just wanted to add to what philly said, Tell your sister to be cool and avoid those ghetto rats at all cost. She is already homeless and needs you more than you need her especially since you've already done her a good deed by giving her a roof over her head. Getting you kicked out is no way to repay you for your kindness. Give her tough love she needs it!