Is it worth paying for Grad school?

I'm a recent college with a biology degree. I cant find a job with this degree. so i want to go back to school to pursue something else. Like Physical Therapist. But the program is 3 yrs long.... summer, fall and spring. I want to do it soon but ill be like 29 before i can start the program. I just turned 27 yesterday. I also have two kids and undergrad student loan to pay back. I ONLY MAKE ABOUT $24,000 A YEAR IN A ENVIRONMENTAL LAB. WHAT TO DO? IS IT WORTH GOING BACK TO MAKE A FEW THOUSAND MORE BUT BE MORE IN DEBT?