There are two SiteSee App License Plan types are available, the difference is as follows:

PRO:
limited to 1 drone 

Supported Drones: Spark (with RC), Phantom 3 & 4 Series , Mavic Air & Pro, Mavic 2 Pro & Zoom, Inspire 1 & 2,
Not Supported Drones / RCs: P4P RTK, Mavic 2 Enterprise, m600, m210, m200, m100
unlimited pilots, unlimited flights

BUSINESS:
limited to 5 drones 

Supported Drones: Spark (with RC), Phantom 3 & 4 Series , Mavic Air & Pro, Mavic 2 Pro & Zoom, Inspire 1 & 2,  m600, m210, m200, m100   
Not Supported Drones / RCs: P4P RTK, Mavic 2 Enterprise
unlimited pilots, unlimited flights

PAYMENT OPTIONS:

You can chose a monthly or annual billing plan and you can chose to cancel the subscription at any time also from within the Account Management page in the SiteSee App (but without refund of remaining purchased period).