Does each additional dog warrant extra time, or is it all done at once within the 30 minute block?

It is ultimately up to you and the owner to decide. If two dogs can be walked at the same time, I'll walk them both together during one booking. If they needed separate 30 minute walks, that would be two different bookings. For drop-ins that don't involve a walk, 30 mins is generally enough for up to 3 or 4 dogs depending on the type of care they need. It is up to you to set your pricing structure and decide if you want to offer 45 minute or hour long visits as well and how much you want to charge for them. The standard walk/drop in on Rover is 30 minutes. During the meet and greet you can clarify with the owner about how much care the dogs need, if they need to be walked or fed separately, and if they need you to stay longer than 30 minutes. Then you can adjust the price in the booking accordingly.

It really is up to each individual sitter. Some sitters will charge the same amount for the second pet (in which at that point I would expect the time to extend)But for sitters who only charge a small additional fee than I feel the 30 mins should be fine.

At the meet and greet you want to make sure to address this with the owner. Find out what their expectations are.

I've only done check-in for three cats since signing up. There was more to it than run in, clean litter boxes and dump food. Since there needed to be specific things done for each cat as far as food went and one needed to be out of his room only when I was there, I charged a discounted fee for two of them and stayed as long as I could manage at the particular time to play with them, pet them and allow the one cat as much time as possible out of his room. It allowed me to make the shiest of the three trust me enough to come and snuggle up against my thigh on the sofa, so I don't feel it was bad practice to charge for the other two.

I'll likely maintain this as my regular practice since even walking two dogs can be more complex than just walking one if they aren't at the same level of training.