What type of contract is required when offering a service?

So I started a small business offering a service that is provided through-out the month and is billed monthly. This service could be stopped at any point, but I want to make sure the following are clear between us and our client:

• Price
• Deliverables and when to expect them
• What is included and what is not
• Payment schedule

What type of contract should I use? Do I have to use a contract, or any document with a signature at the end will be good enough?

No you do not have to require a contract or signature if you do not want to. You can spell out your terms on a page with terms & conditions, and clearly indicate it is month-to-month. Remember, a contract is any accepted agreement with a consideration (payment), whether verbal or written. A verbal contract is just as enforceable as a written one, but doesn't tend to be disputed as often as there is less likely a recording or witnesses to the agreement. If your service fee is nominal, it is unlikely anyone would even bother to sue you even if you breach the contract, as it wouldn't be worth their time.