This is a common question with a complicated answer. In order to qualify for SSDI or SSI disability you must be found disabled by the Social Security Administration (SSA). In addition to being found disabled, you must either have limited resources/assets (SSI) or have enough credits from your work to be insured (SSDI).
SSA defines disability as: as the inability to engage in any substantial gainful activity (SGA) by reason of any medically determinable physical or mental impairment(s) which can be expected to result in death or which has lasted or can be expected to last for a continuous period of not less than 12 months. Found here.
SGA is roughly defined as earning $1,260 (2020) a month (this is for the non-blind). The next question is: can I be found disabled if I make $1,259 a month? Based on my experience, that would be a no. Even coming close to the $1,260 may create an inference that you are capable of doing more and may equal a denial.
If you are not working, it must be determined that your illness is what stops you from working. SSA uses a five step process for determining you are disabled called the sequential evaluation. The sequential evaluation is discussed here and here.
If you can not work anymore because you are sick, apply for SSA benefts as soon as possible at your local SSA office or online. Waiting to file could mean losing benefits. Can you qualify for SSDI/SSI disability? You will not know if you qualify for benefits unless you apply.