Non-liability release form..
Let me start by saying I am not an attorney, but I will share with you what I do know.
As a minor, under the age of 18, should anyone get sued it would be your parents and not you directly. Not only because they are your guardians but because what lawyer is going to sue a self-employed teenager instead of wage-earning adults? (they always go to the 'deepest pockets')
Second, while I know of no "non-liability release" that I could give you here.. what you could do is ask your parents to visit a local workout gym or babysitting company in town under the guise of "looking into babysitting care" and have them ask for a liability waiver because they'd like to review it first.
Now you can use that as a basic 'draft' to create your own (simpler) 'liability-release' form that covers the same basic situations and limitations to the service you are providing.
As a final thought, even
with a liability release form signed by the parents, as a minor you are not able to make a legally binding contract (that I know of) and so it may be your parents that would have to sign along as your representatives. Also, having this signature is not going to prevent parents from at least "attempting" to sue you for civil damages if their baby ends up drinking the bleach or drowning in the toilet under your watch. But it may, in court, help your case rather than if you didn't have anything in writing for a defense attorney to work with.
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Geez, whatever happened to the good old days I hear about when you could just earn some extra cash without a legal team? When did an accident suddenly become an 'accident' that includes liability?