the block 's four apartments are now on the market with the auction date set for april 28 .
listing agents say the apartments are worth between $ 1.3 million and $ 1.5 million .
apartments will be open to the public on april 11-12 , with thousands of people expected to turn up for a look .
contestants keep any money made over their reserves and the team that makes the most receives a $ 100,000 bonus .
agents have started showing potential buyers through the chic three-bedroom properties in trendy south yarra .