Selling life insurance during summers only?

Okay, hear me out… I’m a teacher looking to earn extra income. I am comfortable selling and actually enjoy the challenges of cold calling. I don’t plan to pay for warm leads so most of my business will come from targeted cold calling. I don’t expect to make much money the first few years but, assuming people continue to renew, could I eventually build a book of business that would generate 20k per year on residuals? If so, what’s a realistic timeframe to make that happen?