The vital question here is, is the unit to be separately metered? If not then it is a relatively simple process of running a cable to the existing installation's switchboard. Otherwise...
Where are the meters located? In units there should be one mains cable off the street connected to a meter board which houses all the meters and fuses for each unit. To connect that mains cable is quite expensive.
Just for the connection (which you'll organise with an electrical contractor) you're up for a truck appointment with the distribution company which is in the vicinity of $250, an electrical inspector has to be present which is another $100 and the electrician's time which would probably be another $250, so I'd say you're up for about $600. Some electricians might charge more because it is a bit of a hassle organising the 3 contractors to appear all at the same time so there is a lot of dead time that you will pay for, even though the connection itself might only take 30 minutes.
If on the other hand the meters and street mains have already been installed you may be able to get away without the truck appointment but you'll still need an electrician and inspector.
To run a wire into the unit, how long is a piece of string? Is it underground or overground? How many meters between the unit's switchboard and the meter board?