Having an alternative host

Hi

I have two related questions:

1) I work freelance for a very small charity running workshops. They have paid for me to have a Pro account. I want to be able to make someone else in the team a co-host in case I have technical issues or am unwell. The person has a Pro account also but our accounts are not linked so it won't let me set her up as an Alternative Host. Is there a way round this?

2) I also work for another 3 person organisation. The owner has a Pro account. I want to be able to step in and host their Zoom sessions just one or two months a year. What would be the best way for us to enable this to happen? 

Many thanks