John beat me to it. If you are going into people's homes, you will improve your chances of gaining customers if you are Bonded, and insured.

Here is a link to the pet sitters association, just one of many, with some ideas for you.

http://www.petsitters.org/

I haven't had someone come IN for . . . almost 10 years. Back then, the person I used had to come meet me and the pets before the first time. She insisted on that. She had a form we completed together, included:
- pets names, ages, male/female spayed/neutered
- I had to show proof of current rabies and she would check that box for each pet
- what food I used, whether the pets were on free feeding, using a feeder with a timer (and she made sure she knew how to operate it)
- what water dish, using water from the tap? (I was using water from a Brita, so she had to know to go to the fridge, and fill it again so it was ready forher next visit)
- location of litter boxes, scooper, and location of plastic bags
- location of trash (she was taking it out with her and putting it in the dumpster in the parking lot)
- if any rooms were off limits to the pets and had to have doors closed (I didn't do that)
- she needed a key, naturally, or a plan for me to get it to her when I needed her
- pan how she would return key to me at the end ( do NOT leave the key on your last visit. People's plans get derailed, flights get canceled, snow stops driving, and you may need to go in one more time after all!)
- she insisted payment be left for her. Once I was leaving for 3 weeks so we agreed I paid half up front, and the rest when I picked up the key.
- name address and phone number of my vet; and she had a standard intro letter which she had me sign, authorizing the vet to treat my pets if she brought them in, me to pay, so the vet would know what was going on. We never had a problem.

Here is the link to yet another group:
http://www.petsitters.org/

And this one says it offers forms:
http://www.petsits.com/

If I think of anything more, I'll return to this thread. Hope this helps!