Your post really piqued my interest as i am currently in the midst of the planning process on a block in moreland council into 11 apartments over 3 levels.
It has been a long process (and i haven't even started building yet!) but what i would say to you that it is very difficult to work out a feasibility unless you know what your actual yield will be, ie how many apartments and what size they are.
Consultants fees for this type of development will be well in excess of $100k and possibly up to $200k if you go right through to the building stage so it is important that you get the right advice early on.

I would first contact an architect who has done similar things to your vision in the same area. Look around and see what's happening about the place and then find out who's designed it. Make sure you look for a streamlined building with simple lines, don't go too complicated as this will just add cost. I could recommend someone if you would like.

Your architect will then look over the site and in conjunction with a townplanner (it would be wise to get a good one on board from the start) work out what they think will be achievable for the site. If you are happy with their proposal they will then organise a pre-app meeting with the council planners to see whether it would be supported or not and then you go from there.

Its a slow process and can take up to a yr or more from first meeting with the architect until your permit is issued.

But if you've got the right site in the right area and you stick to your guns you will do really well out of it.

Good luck with it all and if you need any help or advice i would be more than happy to give you a hand.

Cheers
Morty