I'm looking at starting a sales business and need to find out if it's legal under Commercial Law for me to buy products wholesale and then re-brand them with my business logo, etc.
You would need agreement from the wholesale supplier to repackage their goods as yours.
If you are buying goods in wholesale quantities,
why not speak to the supplier and see if they will do an order with your label on the product?
What type of goods are you looking at selling? Some suppliers of electrical products will supply goods as 'white label' products meaning you are allowed to put your own brand on the goods. Then you get into issues around warranties to customers e.g. Is it manufacturer warranties or your warranty you into to pass on to customers?
You can add a price tag or some similar thing.
You might also reasonably add a sticker that identifies you as the retailer - "Bought From Penguin's Tea Shop" - or somesuch.
What you do have to do is avoid giving the ordinary customer the idea (even unintentionally) that you are the maker, when you are not.
That could end up being misleading and deceptive, and so be in breach of Clause 18 of the Australian Consumer Law.