I used my InReach for helicopter extract from a wilderness elk hunt last September.
Concur with changing contact info if you loan it out.
The Garmin subscription is for the device. The subscription merely pays for someone at the other end to coordinate a rescue (for anyone) when the SOS button is pressed.
The cost of the rescue is unrelated to the SOS function of the Inreach.
If you have additional rescue coverage it is for you, whether it is Garmin's or Global Rescue or the like.
Cost of rescue is a function of the state you are rescued in. I was rescued in Wyoming, where all rescues are at no charge to the rescued individual. I learned that after I was rescued.
You can see my rescue on YouTube.
(I made this clip for the Teton Count SAR)