Working on Disability

If I work but make less than the allowed $720 what are my responsibilities to social security. I understand the trial period information but it reads as if it only matters if you make more than the allowed $720. I am in a financial bind atm where I need to either do some cash work or take a part time easy job that I can hopefully handle with my heart condition working 10-15 hours a week. Most of the work available to me that I might be able to perform pays $7.25/hr which is minimum wage here. even working 20 hours at that rate my gross income for a month would be along the lines of $580 so I am curious how this affects me or if I even need to worry about it.

Does this trial period start regardless of how much you make or is it only if you make $720 or more that triggers it? The SSDI documents on the SS website are not that helpful for this question and getting to a human in my area is a nightmare.

Thank You,

Mike