I'll explain it the way I understand it simply so that we don't have to go thru a bunch of scenarios. *ALL* drone flights require a part 107 *except* if you are strictly flying for fun.
Helping my friend is not equal to flying for fun so it...
You don't need to see him remove it but adding your account prior to completing the sell would be ideal.
In addition to the [non]-warranty, it appears DJI Care Refresh hasn't been added to this particular drone so it may be an option for you to...
Imagine all the millions of dollars that could have been saved over the past 3-5 years had it not been for things like tariffs and changes in shipping practices and kitting, common carrier fees, returns, support questions, credit card billing...