OP here. Thanks so much for the help in thinking this through.

We have a beach condo we rent out. We have a smart TV and guests use their own subscription accounts. The WiFi password is completely different than the password for the account.

You set up a separate guest account on your WiFi with a password that you share with renters, for them to use while they are there. You should be able to do that from your account on the xfinity website. That should be a different password than your Netflix and amazon, etc.

I don't think you should let your renters use your subscriptions unless you can control the level of access they have to make password changes or purchases.
We have logged in to our own Netflix subscription at the beach and used it. Can you make the apps available and renters can use whatever ones they have at home to supplement cable or whatever basic TV you're offering?
For the wi-fi I don't know specifically how you'd set it up, but there must be a way. If you use the wi-fi at Starbucks or a hotel you're getting access but not at an administrative level, right?

Amazon Prime has a "PIN on Purchase" option as part of its Parental Controls, so that a PIN is required to make an in-app purchase. I would imagine that Hulu and Netflix have something similar.

A renter shouldn't be able to see or change the passwords for your Amazon/Netflix/Hulu accounts if all they have access to is your TV. They shouldn't need to have your Amazon/Hulu/Netflix passwords in the first place if the apps are loaded on your TV or Fire Stick or whatever, so they can't change it. I had to change my Amazon password recently, and I couldn't do it on the Fire Stick. And enabling Parental Controls should also prevent that.

As for the wi-fi, I don't think you need to change the password every time, although you should change it from the factory default, and it's a good idea to change it from time to time. People can't log into to your wi-fi unless they are within range, so unless they live in town, drive over, and park right outside the window, knowing the password
won't help them any.

Xfinity should have instructions about changing the password to the wi-fi, and it should either require the router's admin password, which you should not give to guests, or logging into your Xfinity account with your username and password, which you should also not give to guests.

I recently bought a property in a beach area that I will be renting out on a weekly basis.

The property has wifi through xfinity. I regularly watch Netflix, Hulu and PrimeVideo on the TV there.

Right now, the password we use for accessing the wifi is the one printed on the router label. Can someone help me think through how we should handle wifi access when we have renters? We want our renters to have wifi. But is it a bad idea just to keep the same password (from the router) or should we change and update it with each rental? Why or why not? And if someone has the wifi password, how can we keep them from changing it to something else, thus locking us out of our own system? I assume we should make sure there is some sort of two-step authorization?

And similarly with Netflix and Hulu and Prime Video...I'm happy to let our renters use those BUT I don't want them changing our passwords or purchasing anything. How do we allow them to use our subscriptions while not allowing them to access our accounts?

I don't want to learn a hard lesson where I let someone use my PrimeVideo but find out later that they bought $2000 worth of stuff from Amazon or they have been using my subscriptions from their own homes. I'm sure there are plenty of folks on here who have BTDT and I'm hoping you'll be willing to share. Thanks.