Does Form 944 applies if I want to file i-130 to get a green card for my mom? Also what income i have to have to support mom if I'm a single mother?

Yes the 944 has to be completed. Every case is unique as to the level of income needed. It depends on the household size and the state you live in, etc. Are you a US citizen and did mom enter the country legally. Discuss with counsel. Counsel anywhere in the USA can represent you. Some of us charge a very affordable flat fee for representation from start to finish.