In order to have a ridesharing policy with a standard car insurance company (such as Geico or Progressive), you have to have a personal policy already established. A personal policy is what the average driver in the US currently has. Unfortunately, a horse taxi company would not be considered this. I can only assume that would be considered some type of commercial policy because you are profiting from it. What you can do is get a personal policy, add a rideshare endorsement, and add your commercial business to the company. Many large insurance companies offer commercial policies as well as personal policies. Although I am not sure if you will get a bundling discount for this policy because I'm not licensed for commercial policies. Here is some information regarding ride-sharing policies.