Option Contract - How to do ?

[Jason Dinh]

Good day everyone ! I'm Jason from Melbourne (VIC), Australia. I have some questions about Option Contract when selling a property. The situation is, I specialise in OFF MARKET sites where all my purchasers are Investors/Developers. They love something off market and good deals. I often obtain many sites and sell to them. However, I just found out that I can sell a better price than what I have deal with vendors. So, if I want to do this, then:

1. How do I sell the site with higher price by not letting Vendor knows about this ? from this, how can I avoid the final price in Contract of Sale ? and How do I get the difference ? 

2. If the Vendor agrees that I can sell whatever price as long as he gets what he wants. How do I secure and get the Difference from Vendor ? 

3. If I can do this, how do I get away with Stam duty and Personal/Company TAX for the deal ? and How to help the Vendor avoid / minimise the CAPITAL TAX?

Thanks for read/answer my questions.