A home exchange is a non-commercial arrangement, so each home owners pays their bills as they normally would. Agree beforehand who should pay additional expenses such as long distance telephone calls.
The only exception to this is if there may be a large disparity between the two sets of bills. For example, air-conditioning can be expensive so some members add a 'reasonable use' request to their agreement.
If a car-exchange is involved you should sort out insurance and liability in the case of fault and no-fault accidents.