Cancel Lease w/ Tenant Asking for Radon Test Before Move-In?

[Art Maydan]

Had a tenant sign the lease and send the move-in fee and 1st month's rent then start asking a bunch of super high-maintenance questions. My favorite is, "Do you have a radon test for me? No worries if not. I can get my own." So he intends to move in, run a $15 Home Depot radon test, and move out if he gets a false positive or reads the test wrong or whatever. Regardless, it speaks to him being a high maintenance person I don't want to rent to. I cancelled a lease once before move-in when it became clear the lady was going to AirBnB it. Just sent her back her money with an email saying her lease is cancelled due to an obvious impending lease violation she revealed in her communication. What's the legality of doing the same here?