(1) Before commencing work, I think there is MUCH you MUST know about how working affects your benefits.
(2) Unfortunately, unless I am mistaken, there is no one at your local SSA office who knows or will tell you in detail about how your job earnings will affect your SSDI and Medicare (I'm assuming you have Medicare; I'm going to assume that you don't have Medicaid).
(3) The laws and regulations about how job earnings affect SSDI are VERY complex. If anyone says it is simply and "easy breezy," they are either lying or misinformed.
(4) First, you absolutely MUST report your earnings each month. Last time I checked, in 2011, the SSA did not have any official form for this reporting. But check the SSA web site. Maybe they do now. In any case, this is what I did. On the first work day after the end of the month, I submitted, via certified mail, a copy of pay stubs showing all the earnings EARNED during the last calender month. I'm about 90% sure they want a report of what you EARNED in the month, not what you RECEIVED. If you worked 20 hours in a month, and were working at a rate of $10 per hour, you earned $200 in that month, and so report that, even if they didn't pay you some of that until the next month.
(5) If, ever since you've never been on SSDI, you've never worked before this job about to begin, you will get a 9 month "trial work period." During those 9 months, you will continue to receive your SSDI check, regardless of what your earnings are. However, if staring in the 10th month, you earn $1,070 or more, your SSDI checks will stop. However, your Medicare will continue or can continue for a certain period of time. You'll have to contact Medicare about that, or research it on the Internet.
(6) The SSA has various "work incentive" programs. One is called "Ticket to Work." They are all pretty complicated. I can't explain those here. The best thing you can do is try to research them on web pages. Most people who claim to know about them really don't really understand them. They are VERY complicated.
(7) Here's the biggest truth about working when you have SSDI, a truth that hardly anyone will tell you, and which many people will vigorously dispute: If you are on SSDI for a psychiatric illness, working puts you on track for permanently losing SSDI and Medicare, and for losing your status as a person with a disability. Why is that? Because under the federal law, which the SSA much follow, a person has a disability if he/she is unable to do "substantial gainful activity" (called SGA for short) due to a serious medical condition. Working, even part-time, is evidence that the SSA will use to review your case to determine whether you have undergone "medical improvement" such that you are no longer "disabled" under federal law. Many, many people think that as long as your psychiatrist continues to diagnose you as Bi-Polar, Schizophrenic, etc., that you are disabled and cannot lose your SSDI. UNTRUE! The SSA is required by law to review each disability case every few years. These are called "Continuing Disability Reviews" or "Medical Reviews." But they don't just review your medical records. They ALSO review your work history! That's a fact! It is required in the law. Working is the opposite of disability, especially for those whose disability is mental illness. People who have blindness or paralysis are safe. They can't lose their SSDI by working, except in rare cases. Also people with Developmental Disabilities can't lose their federal disability benefits by working. But SSDI recipients with mental illnesses can!
(8) So, in my opinion, someone one SSDI should go back to work, if they are able to, provided that they and their psychiatrist (and their social worker if they have one) believe that he/she had recovered enough to FULLY support themselves by work, by working full-time. Part-time work on a permanent basis is not compatible with SSDI for people whose disability is mental illness. For such persons, working is a path to the end of SSDI and Medicare.
(9) There's lots more to this. I haven't been able to cover everything. I have worked three jobs since going on SSDI for a mental illness. Plus, I was employed by a community mental health agency to advise SSDI and SSI recipients on how working would affect their benefits. I received several months of in-depth training in all the SSA laws and regulations. There are lots of web sites that explain all of this, but I must warn you. Many web sites mis-explain things. Even some of the SSA pamphlets and web sites are worded in ways that, in my opinion, are misleading (though not outright incorrect or false). The SSA wants people on SSDI to go to work because they are under intense pressure from Congress to get SSDI beneficiaries "off the rolls." In other words, they want you to work because they want your benefits to end. And, that is a good thing, provided your psychological impairments are not so severe as to prevent you from fully supporting yourself by work. The workers in community mental health agencies promote working for SSDI recipients, because the whole mental health system has come to promote work as a means of "recovery" for people with mental illnesses. Well, work can be therapeutic, that's true, for some or many people. But if you really are never going to be able to fully support yourself by work alone, then working can or will end up being a catastrophe. So, in sum, I encourage you to read lots of web sites about "SSA work incentives," "Ticket to Work," "Continuing Disability Review," "Substantial Gainful Activity," "Medical Improvement," and so on. If you are not good at understanding complex laws and regulations, maybe some relative or friend of yours could help you with this research. I just want you to make an informed decision. There are, in my opinion, people out there who are intentionally or unintentionally misleading SSDI beneficiaries with a mental illness who are thinking about going to work. Exercise good judgment and common sense. Nolo Press has some books and web pages on SSA disability law that you might find helpful. Good luck.