How do I project how much income I will make with a startup? I know how much money I make with my current full-time job and how much I need to continue paying the bills. I know how much I need to charge per hour for the services, I just don't know how quickly I will have paying customers needed to reach the income goals I have set. How do I figure out how quickly things will progress once started? I know that unrealistic goals will only cause frustration while not helping the business.
It's very hard to guess -- a lot depends on the price you are charging for whatever the services are, how many competitors are offering the same thing and how easy/difficult it will be to target the right customers. I would not go into it thinking you will immediately be making money. A lot of founders don't even take a salary for the first year or so. You should be prepared for some time period to build the business during which there is low/no salary...maybe you can start it on the side?