Need To Move With My 3 Kids by September

I desperately need to move from my small apartment. I have 2 girls and a boy. Need to move by September, The place is to small for them to stay in. My daughter will not be able to legally be able to live in the same room as my son because she is to old to share a room with a boy. I don't have enough for a first and last rent and a security deposit. I found a 3 BR for 1250 a month. I can afford to pay the rent after. But I don't have the money to ensure that I am able to move. If anyone can help I'd be so grateful, I want to see my kids in a safe home. Where I don't need to worry about mice, bugs, and other broken things in the house. Which the landlord has not bothered to call someone to look at the stuck windows, and below average plumbing for months now.