Salt. One of the main causes of water retention is eating too much salty food. The main component of salt is sodium, which the body dilutes with water if too much of it is present. Salt makes you thirsty, and your body will hold on to this water.
Or reject it, or counter-offer your terms. Usually you should hear back from the seller within 2 days, unless the seller is a bank (foreclosure) in which case they can take up to 10 days to get you a response.
When would you like it to be done, you are paying for it, ask for it to be done within 48 hours, I don't understand why your Agent hasn't told you how long it will be, as for how long does it take, well part of the appraisal is research before seeing the home, then the physical visiting of the home to verify features and see actual condition of the home.