There is no legal obligation to provide reimbursemenbt for meals, mileage, rental cars, hotel, etc.--it is common to do so, but not required. And if you will provide reimbursement, you may set limits (i.e. only up to $15 for a meal; only a $35 per day per diem, which the employee may spend as he/she wants; etc.) or other requirements (e.g. no reimbursement without receipts). You do need to pay for their driving/travel time, however--that is work time, because it is time spent on mandatory travel to a work event.