TBH I think buying before selling could be quite risky!!
I have a friend who just did that, bought a new house subject to the old one selling, moved into the new house and their house didn't sell so they had to give up the new house they were already living in, sold their old house at a loss and now have had to buy something different.

BUT if you think that another house won't come up and yours will def sell maybe see if you can buy on conditions that your house sells?