working or getting paid?

I have no idea how this stuff works. BIL has a fairly serious health issue that has kept him out of work for a month or so. It’s been determined he needs surgery but the doctor can’t do it until January. FMLA runs out in a few weeks and he’s not physically able to go back to work.

No savings. No assets. Liabilities really only rent, car payment, and child support. He’s afraid of losing his apartment which is below market rates and falling behind on other payments.

If he isn’t let go after FMLA ends can he get disability?