Nope! Rover makes their money when you do - they get 15% of what you charge your clients. There are services you can pay for, such as the protection package, but that appears as a negative balance on your profile, so instead of paying out of pocket, it is paid off as you begin to book stays. When I began, the only money I paid up front was for my background check (I know for a time they were being offered free, but I'm not sure if that's still the case), which is not required, but it is helpful in starting out and attracting new clients.
When you're putting together your profile, I recommend putting up lots of high quality pictures. You want people to feel comfortable with you even before they meet you, and you want to make pet owners think they're dog will enjoy her time with you. Have one or two people go over the written sections of your profile to proofread for spelling, grammar, etc. Since this is a business page, you want everything to sound professional, but still be warm and friendly. Finally, earn as many badges as you can. They'll help you climb the search rankings, which will get you more exposure to new clients. Then put the word out to draw people in!
Good luck-