When we consult we do an hourly rate. The rate will depend on the type of consulting. Your time and your knowledge are valuable so it would not be like an hourly wage. They aren't strictly paying you to work for them. The rate will vary based on your location and how involved the issue is. Some people charge as low as $25 per hour and some are more like $250 per hour. Personally I would not go lower than $75 an hour myself because my knowledge is worth that much. You have to value yourself and make sure you price yourself accordingly.
The contract for consulting is much shorter than a billing contract. It should simply spell out what you will be doing, what you will provide, what you need from the client, and when the work will be done. It should also include a statement for HIPAA purposes (stating that you will protect any PHI you are exposed to and that you will only use it for the purposes of the consulting). Each contract for consulting will vary depending on what you are doing.
Hope that helps!