Hi @Ashley1783 ,
I have been hosting for 10 months now. My situation is similar to your as we live just below our tenants in our 2 flat. We do share our wifi password and my husband (IT nerd :-)) felt it would not be a problem. Actually for the guest it is much safer than using a public wifi, say at a coffee shop.
If one logs in it only covers for a certain distance, in other words it would be of no use to anyone outside of our network area.
For my private information that is part of our wifi, logging in like banking, etc. I always use 2 step verification and would highly recommend doing that yourself if not already.
I have had over 50 guests and we never incurred a problem.
Good luck,
Possibly others in the group might have conflicting concerns or reason not to.
Happy Holidays,
Bettye6