I am working on a psychology research study which requires follow-up interviews with low-income participants. We encourage our participants to meet with us at our research facility for these interviews in person, but sometimes they are unable to come in and we will conduct the interview over the phone. The trouble is, most of these people have a limited number of minutes on prepaid phones which they do not want to use up. As we are asking them questions that are personal in nature, such as recent sexual and self-harm behavior, the participant cannot typically call us from any public land line. Most of these people are homeless and do not have computers, so any sort of VoIP is out.