We sometimes get questions about doing radon tests. Like any kind of contingency, it's possible to have a radon contingency in the contract.
Few home buyers do this, although in the 1980's, Radon was a hot topic and frequently tested for.
The type of structure can have an effect on the amount of Radon in the house. For example, if you have a below-grade basement with poor ventilation (no walk-out, for example), you may have an increased likelihood of having higher radon levels than if your home is completely above-ground. However, having said that, just because your house is above-ground does not mean you are guaranteed not to have a radon issue.
You can read this information for more details - here's an excerpt:
Are radon levels affected by the ventilation in my house?
Yes. Sometimes radon concentrations can be reduced to acceptable levels by increased ventilation.
This is also a great FAQ on radon.
We find that only 1% to 2% of our clients do a radon test, but we've started encouraging clients to do so.