Today, if you're at all serious about succeeding in any endeavor, whether online or offline, you have to deliver enormous amounts of value. Yes, you have to do the most amount of work for the least initial return. This is especially true online. Why? Because it takes time to build authority and create an audience, two primary ingredients necessary to succeed in the wonderful world of commerce on the web.
One factor that you must be aware of though is that Care.com is a peer-to-peer arrangement. That means that you will be in direct competition with other pet sitters in your area. You must price your services competitively in order to get business. Once you begin to develop a list of regular clients, you will be in a better position to raise your rates. This will be particularly true as you get referrals from those customers.