The radon test is optional for the buyer and I have negotiated several mitigation systems in the past, which is not relevant to the original question.
The inspectors I recommend always conduct a 'radon test'.
The properties that have come back with high radon levels, I've always worked to negotiate the seller pay for the $1,500 to $3,000 remediation system. The seller has always paid for it, however, this is not mandatory but a point of negotiation.
Find yourself a strong negotiator for an agent as well as a good inspector & lender! You'll make good decisions that way!
Good Luck with your move to north Idaho!
At YOUR service...
If radon is a concern for you, make a radon test showing the home is under EPA guidelines a contingency of the sale.
Best of luck!
The EPA site here has some more info on Radon in the state of Idaho as well as some contact info.