yes you will have to pay stamp duty and 100% CGT as it is under a year (contract to contract.)  We nearly did this last year and it would have been profitable but held on to it for longer (after settlement) and have recently sold.  We were in an up market then and our settlement period ended up being over a year because of a subdivision which had to go through first .  Now it may not work for you depending on the area, it would need to be a fast growing area and you would have had to have bought well and be sure of getting your required sale price. best wishes.  Colleen.