A $50,000 budget is on the tighter side for a house extension in Australia, but it is not impossible depending on the size and scope of the work.
At that price point, you are generally looking at a small addition of around 15 to 20 square metres with basic finishes and no major plumbing or electrical changes. A simple studio room, garden room, or modest living area extension might be achievable within that range in some markets, though costs vary between states and regions.
Keep in mind that in Sydney and other major cities, construction costs tend to be higher than in regional areas. Being realistic about what is achievable and prioritising where the money goes is key.
Mitroteam Projects can help you scope a project that works within your budget without cutting corners on the things that matter.