Landlord electricity calculator

I have multiple properties. In these properties, i have multiple tenants. Each tenants has his own electricity meter. At end of each month, I read the meter usage of what they have used. The council gives me one bill for the electricity. I divide the bill by the electricity usage (derived from the meter readings) I then invoice my tenants. 1- I need a web based (mysql) program (with secure login) where I can enter my properties, tenants within these properties with their contact details, rental paid, expiry date of lease, and upload the copy of their lease. 2- I must then be able to every month enter the current meter readings, it must check the previous months reading and calculate the usage for the month. I must then enter the property council invoice total, and the program must work out how much the tenants must pay according to their usage. 3- All this info must be saved in the database, so when i want to go back a few months to see the figures, i must be able to view it. 4- If the program can output to an invoice, all good. Remember, it have multiple properties (like blocks of flats) and many tenants in the property ( many flats within the block of flats). I receive one total bill for ALL the flats in the block, of which I have to separate the usage based on meter readings. my skyp id is illuder