Scenario: Legally turning 2 buildings into 1.

Hi,
I’m trying to find the best solution for the following scenario, any advice would be greatly appreciated:

SCENARIO

My most recent purchase has 2 dwellings approximately 2m apart.
I would like to join them both up in order to pass it through council as one dwelling so I may construct a granny flat on the back of the property, as there is more than sufficient land.

My thoughts are to use brickwork to essentially join the two dwellings, add a sliding door to the outside between the two properties, perhaps tile the floor and cover the roof area in between to look like a sunroom. The house is made of bricks, the second dwelling is a mix of cladding and wood, I would essentially be bricking around it, there are 6 existing wooden beams connecting the two buildings superficially, with a fabric used as a cover. Structurally the buildings are fine, though a small section of the second dwelling seems to have low roof, nothing that can’t be changed (i’m an engineer and took a builder with me to inspect).

Although both dwellings are on the sales contract, I am suspicious of how much of it is actually legal.

QUESTIONS

1. What is the best way to find out how much of the building is legal, without incurring the watchful eye of council before any work is done?
2. Is any of this necessary or may I just claim second dwelling is a shed (no, in built kitchen, although there is a bathroom)?
3. Would the idea of essentially turning the space between into a common sunroom be sufficient to approach council and ask for approval of an existing illegal construction?
4. How many electrical connections may I add to a building? I already have a tenant for the property at the front upon settlement, and am thinking of living in the second dwelling myself, I would need to add a separate electricity line.

More questions to come, still in the thought of turning an idea into reality :p

Thanks again.
NHG