How much should I be afraid of Personal Service Business audits from CRA?

I am a software engineer and recently got a contract opportunity. When I looked into the incorporation rules and tax traps, there is a high risk of being audited as PSB by CRA if I only have one client.

Does everyone who work on contracts and take profits via T5, have more than one client? Its hard to find multiple clients to work for at the same time. What if I work for a client till October and the found another client on December, essentially only one at a time?
Taking out salary via T4 is my last resort, which i don't prefer doing.