The visits should accommodate your schedule. While the employer has times he would like for you to visit, if your schedule cannot allow for it, it is appropriate to ask to reschedule for a more convenient time.
Companies generally pay for travel expenses associated with an on-site interview visit.
This usually includes air or train fare, hotels, meals and cabfares required. However, it is best to verify that they will pay before you incur expenses. Before you leave the office visit be sure to ask who you should send your receipts to and get a copy of the proper forms needed for reimbursement. Remember to keep your expenses within a reasonable range. Absolutely do not double charge two or more employers for the same trip.