We have a pretty simple setup. One product of "15 Day Free Trial then just $14 Per Month". How can we create a coupon code to give our users 50% off of their first bill after the free trial is over? But not recurring to every month? Just month 1.
Such set up is not possible. You can set up coupon to apply discount either only to first payment or to all - first and subsequent payments. In your case first payment is 0 (free trial). You can set up two different products with same access '15 Day Free Trial' and 'Paid monthly subscription'. In this case your scenario is possible for paid product. Just set discount to 50% and disable option 'Apply to Recurring'. Also you may want to restrict ability to purchase free trial second time. Please check 'Product Availability' settings in product edit screen. Best Regards.