If you have a substance abuse problem that requires you to go to rehabilitation you will likely have to be admitted to the facility for 8 to 12 weeks. Please note that your health insurance will probably pay for this rehabilitation. However, not all health insurance is the same. For example, if you are allowed to go home on weekends after, perhaps, being in the facility for 6 weeks please note that some health insurers will say that they will no longer pay for the rehabilitation after that occurs. The reasoning seems to be that if you are not required to be in the facility 100% of the time, then you are no longer in need of treatment. This is in my view nonsense, but you should be aware that it might happen.
Also, while you are in the rehabilitation program you are obviously not working and therefore not earning money. This is where your disability insurance policy comes into play. You can file for disability and the payment from the company might well be very substantial depending on the type of policy you have.