First you should have like a stable source of income. An attorney might be best though to answer this.

Financial Sponsors File Form I-864, Affidavit of Support

Generally, the sponsor must prove that they have an income that is at least 125 percent of the federal poverty guidelines based on the household size

The sponsor (U.S. citizen or permanent resident) typically must have an annual income that is at least 125% of the Federal Poverty Guidelines

In my case, I dint have alot of money but I was given a green card

I think that demonstrating you can look after them speaks volumes,its not just about financial stability as well