Here is a nice visual guide to electric service cables from Kingsway Inspections. The left is 100 amps, the middle is 150 amps, and the right is 200 amps. If you are thinking of buying a rental you need a minimum of 100 amps per a unit, 150 ideally. If you have less, factor upgrading your electrical for the purchase as having a lower amp rating will create headaches and tenant frustrations in the long term.
-Mike from TerraVestra Property Management