Your income needs to meet 100% of the poverty guidelines. See this website for the poverty guidelines of 2015:
http://aspe.hhs.gov/poverty/15poverty.cfm
If you don't have income (e.g. no job), then your bank deposit or other type of assets has to be 5 times of the poverty guidelines.
You need to provide the completed I-134 and support documents (e.g. employment verification letter from the employer, copy of tax return and W-2 of 2014, bank statement, etc.).