While I do work Monday through Friday from 8 AM to 5PM CTS, I can find flexibility in those times, if needed. Nights and weekends would be preferable, but I can absolutely be available during the week and during normal business hours as well.
While I do enjoy speaking with individuals on the phone, I find it more personable; I find it almost a necessity to communicate in e-mails these days. It allows each party to have a tangible record of the conversation, as well as the ability to respond at their earliest convenience. With a phone call, you may miss the person and they may forget to call you back.
Payment terms are negotiable to some degree. Weekly, bi-weekly, monthly, or per-job will work for me. It all depends on what works best for you and your needs.