Unit transfer improvements

**Deposit** If a user is transferred and the deposit of the new unit is higher, charge them. If the deposit of the new unit is lower, convert the balance into a prepayment. **Rent** If rental rate changes a result of a transfer, the pro-rated difference should be accounted for in the transfer of the unit. Any paid rent from the preivous unit should also be taken into account. **Charges** If there are discounts associated with the rental amount previously, adjust the discounts accordingly to the new rate. **Unit access** During the transfer process, there would be a period of x days (1~2 days) that the customer should continue to have access to both units in order to complete the physical move from unit A to unit B.