Well there are stamp duty savings by staying where you are but rental cost of somewhere to live while the whole process goes on. Some more thoughts from my Blog at https://anewhouse.com.au/2014/12/reasons-to-rebuild/

Love your Work!

there are numerous Sydney based building companies that offer a KDRB service and many that offer display homes that can provide an excellent starting point for house plans that can be modified to suit.. check websites that have designs (with prices) identified by width of block, size of house (50 squares=465sqm) number of bedrooms, bathrooms and garages for suitable houses and ask for quotes based on your specific site and be prepared for much more than you expect but probably less than the cost of a house needing major renovations that doesn't meet your needs.. and of course you could hire an architect to achieve a truly custom designed home but a few tips would be to obtain a proper site plan showing exact length of all your boundaries, direction of north, locations of services, a detailed contour diagram showing the precise levels of your land and contact local council to find out the maximum size house that can be built on your block and any restrictions for height or easements

Hello Richard, This is a very interesting project and one that I am well placed to assist with. As an architectural draftee my forte' is plans. In your case I could chat to you and your wife about what you want to achieve and ask you 20 questions +-. Then prepare plans for renovations single or double storey and new home on the site. That way once we have tweaked the plans to your liking, you would have two or three plans to take to several builders for comparative quotes and you can choose which way to go based not just on plans and price but on time lines communications, inclusions and your own criteria etc. The answer of which option would be better for you will come clear and it would be based on real plans not just "arm waving". I invite you to look over my website and have a good read about previous works, blogs which will give you an idea of how I think! I would love to hear from you and assist you with this most important project. Kind regards, Margot