One-off jobs and Quarterly Taxes

Hey there, 

 

I never started my own business but for the past 4-5 months months now I have been doing odds-and-ends jobs to the point that it is where most of my income comes from now. I work for an hourly rate and just get a ton of word-of-mouth. There are only a few clients that have paid me more than $500, which I take it is the minimum (so I've been told) before you have to pay taxes on it. 

My main questions are:

1. What of these do I need to pay taxes on?

2. Does the TurboTax TaxCaster help figure how much?

3. If I need to be paying quarterly, where do I insert everything so I can stop worrying about it?

 

Thank you so much for your time and answers!!