At the car lot we sell used cars "As Is", however that in no way protects us from personal injury liability. Our wrenches go through every car top to bottom and repair what needs to be repaired. Brake pads, wiper blades, and tires are always replaced. The As Is thing is simply about a mechanical failure of the product unattached to any personal injury liability.
GET INSURANCE specific to your operation whether it be flipping bikes, tune ups, handyman, etc. An umbrella policy will not protect you from personal liability. Oh, one more thing. Do yourself and your family a big favor. Set yourself up as a small biz. Totally legit with a tax license and all the other heavy handed stuff. When the crap hits the fan you will be set up correctly to deal with it provided you have a competent lawyer representing you.
Disclaimer: I am not a lawyer, nor do I pretend to be one on TV, but I have been down this road once and understand it.