Dear Kim,
Three things that might be of help:
--- Find out at your job if they have any policy in place for living organ donors. The Federal Government and some State governments give medical leave WITH PAY to organ donors, and some (few) priviate companies do so as well.
--- Organ donorsw may not be paid for the organ, but it is legal to re-emburse the donor for lost wages and all financial costs (travel, lodging, etc) connected with the donation. Some families organize fund-raising activities to help the donor with this, and that is quite legal. It does, of course, involve some loss of privacy, but often there are people who are ready and willing to contribute once they know of the need.
--- Keep in mind that some (few) kidney donors do suffer long-term health complications that can result in being out of work for a longer time. So it is wise to have "just-in-case" financial plans in order. They can give you a rough idea of when you can reasonable expect to be able to return to work, but NOBODY can predict with certainty just how much time YOu will need. Each donor is different.
Hope some of this helps. keep getting well informed. Also, make sure that your step-mom's other relatives, friends, neighbors, co-workers, Church/Synagogue members, old alumni, etc. know of her ned. There may be other willing volunteers who are in better financial/insurance shape to donate and would be willing IF they knew of the need and the possibility. Get the word out.
best wishes,
Fr. Pat