We use data from the Fragile Families and Child Wellbeing Study (N = 12,140 person-waves) to identify characteristics associated with mothers' having or lacking "personal safety net" support from family and friends. We focus on characteristics that are likely to increase the importance of having support available but may also interfere with the maintenance of supportive ties: poverty, poor physical and mental health, and challenging childrearing responsibilities. By capitalizing on distinctions among these types of personal disadvantages and among types of personal safety nets (financial, housing, child care, and emotional), we help to explain why personal disadvantages are associated with weaker support. Our paper contributes to the literature emphasizing the importance of reciprocity in support relationships and introduces the idea that families that are more difficult to help will have less support available.