Affidavits of Support can be very tricky to deal with and I would suggest getting an immigration attorney if there is any confusion at all.
Affidavits of Support come up most often when a family member would like to petition another family member for permanent residency in the United States. Under the rules, the sponsor must make the equivalent of 125% of the poverty guidelines. The number will vary depending on how many dependants are in the household.
One of the most common questions is what income can be used for an Affidavit of Support.
Normally you take the income that you take from working, however other income can be used as well. If you have income from any of the following sources, you can include this income: alimony, child support, dividend or interest income, welfare, retirement income, and unemployment through the current year. Income from the person who you are petitioning for will not count unless they are working legally.
A joint sponsor or assets that you own can also be used to qualify you if your income does not meet the 125% of the poverty guidelines as required. Assets can make up the difference of what income is needed. It is best to contact an immigration attorney if assets need to be used. You have to use a mathematical formula depending on the relationship.