I picked up an indoor WYZE camera and it's really feature rich for $30. The outdoor ones are a tiny bit higher, are suited for all weather. They record to local SD card, power by usb or Poe, so super easy to use. Can use cloud storage for like $3/month and more features. I'm sure they have even some prosumer stuff too, I only got the basic one. Their app works well, used it when I was on vacation to check things.
Just avoid RING cameras as Amazon basically gives their employees free reign to look at anyone's footage, employees even searching for cameras tagged "bedroom", etc. They'll also hand over your footage to police without warrants.
Put it on the guest network if your guest network only provides internet access and not full network access to other devices. This is pretty standard for IOT devices.