Invoicing + PayUmoney PG

Hi, I plan to use Geodirectory packages + WPI + WPI PayuMoney PG to collect one time, as well as recurring subscription payments for listings, on my site currently in dev.

However, for the initial 2-3 months after launch, I may be offering a free trial period even for paid listings (using free trial in GD package or WP discount coupon), and so I wanted to defer adding the Payumoney PG for 1-2 months after launch and then set it up before the payments start.

Can you please advise what can be the issues with this model? I suppose recurring payments are triggered as per the schedule, so until the PG is not plugged in (test gateway option selected), the invoices will be zero value and hence not hit the PG. Once the PG is plugged in, and the trial/discount period over, then subsequent recurring payments will go thru PG. Is there any issue with this, can you please help me understand or point me to the relevant documentation?

thanks very much,
Vivek