You determine how you will provide this service, but make sure you discuss this with potential customers. There are many sitters on Rover who will stay at the home, use it as a base of operations while doing walks and drop-ins for other clients, but they stay at the home for a majority of their time.
House sitting as a service here on Rover is subject to the most interpretation. Some perform as I have described; others may only sleep at the home overnight, arriving at, for example, 7 p, and then leaving in the morning at 8 am. Then they might charge the customer to come back for walks or drop-ins. An a la carte approach.
You need to make sure the client knows and accepts how you plan to provide the service. There are some clients who assume that the sitter never leaves at all. If that's the case, then they need to be paying top dollar for that level of exclusivity. Your $30 rate wouldn't guarantee that level of care IMO. So I would say go ahead and book the other services, so long as you are there during all the important times.