Condition the sale contract subject to DA for 2 units (within a reasonable timeframe) and subdivision of the property by the current owner – it may be possible to buy this site using an option contract (small fee which is then included as part of the purchase price if you proceed but forfeited if you don't ).  If you don't get the DA, have a fallback of a lower price. Then there would be nothing too different from buying, getting approval then building.

The qs will shed more light on the matter but if you contact the AIQS (aust inst QS) they have a full list of practitioners. Generally though, anything pre-July 1985ish did not attract depreciation allowances but as they have a remaining life & a current value this may be able to be depreciated.
Google QS's for more info but Napier & Blakeley or BMTQS have some good info on their sites.

As with all insurances, shop around. Some may need to spread their risks more than others and are able to offer better prices in some areas whereas they may have too much exposure in other areas and their premiums are reflective of this scenario.

1 – You'd probably need to ask the solicitor doing the transfer. Her ownership pre-marriage/moving in may jeopardise her chance of getting the FHB grant. She'd most likely have to buy before she moved in with him though.

One difference between Joint Tenants & Tenants in common is survivorship, JT gets the property upon the other parties death, whereas TIC are able to will their portion to someone else. What would be her issue (you can still be TIC at 50%).

2 questions – is there going to be a recontribution of the capital to your friend by his girlfriend or is he putting her on the title for free (stamp duty may not be payable if it is a nil transfer for 'love')?
Cgt may apply if this is not his PPOR, also may apply if he is transferring at a profit (might get a credit if he transfers at a loss).
Will she accept her name on the title as tenants in common BF 99% girlfriend 1%?

Stucco is only render, hit it with a scabbling gun & re-render or take of 4 inch wide vertical strips and lay battens/blue board/render.
Weight should be about 40kg/m2 – do you have about 300 m2 to do? If so you might need to use a renderer to get a decent finish.

They charge you a finders fee (deductible from the $500, or so they say). Signing up to the email gives you free access to the pricing and returns (they send daily emails).
If you look on the net, you will probably find the same properties advertised – they scrub out the agent's sign & any advertising that will identify the property – I have seen some of these sites, more easily identified if it commercial or retail.

The returns indicated are somewhat unrealistic at times.

Google Spiro Kladis & see what you get….

The law of the jungle applies – however it does have many implications: the purchaser can only write down depreciation on the value of what they have bought ie the discounted price, the purchaser will onsell the units at their true market value (not at the heavily discounted/get out of gaol price at which it was purchased), valuers will have to disregard this sale as it was a distressed sale (and may have been off market).

The losers are those who had heavily invested with the developer (unless there was still some cream in the can). The winner will be the buyer of the development (who then holds & onsells the project at market value). The neutral are the mums & dads who will end up buying their share of the property at market as the profit has already been lost, then remade. Depending upon who the developer was, maybe our super funds (ie ourselves) will lose.

Just a few pointers – how many zones are they going to provide ie upstairs/downstairs or greater degree of control?
How many thermostats (one up & one downstairs), does the system have the capacity to cool both levels simultaneously?
Do you need to install 3 phase power or is this included?
Is there access in your ceiling space to install the ducts for downstairs or are the diffusers going to be below your robes regardless of where they sit in the rooms?
Is the roof insulated? (it will pay to get this done as well to make the unit more efficient).

Have you done the cost comparison on using split systems or combining split systems for downstairs & smaller plant for upstairs? This adds to your ability to control the rooms better but will add to your servicing costs.

As for adding value, it won't detract from the house regardless of which type that you install, just make sure that it is effective & don't get rid of the fans as they will supplement the air circulation.