If you suspect someone you love has a drug problem, how would you handle it?

My brother moved out of town about a year ago. He’s almost 21 and lives with a roommate. He used to smoke pot when he was in high school, but I dont know if he used any other drugs. Anyway, he called and asked me for money the other day, saying he couldnt pay his bills. (He’s supposedly working 2 jobs and only pays half of the apartment bills). I told him I would help him if I could but Im not in any position to at the moment. I told my mom he had called and it seems she was the first one he went to but she told him no (apparently he’s ALWAYS asking her for money and she usually gives it to him). The next day I find out he tried to hit up my grandmother for money, knowing that she’s going senial (sp?) and has no concept of money anymore. I personally thought that was very low and completely out of character for him, which now has me convinced that he’s using (The kid has 2 jobs and can’t come up with $400 a month for his share of bills?!?) I suggested this to my mother and she agrees that he probably is on drugs. We are disagreeing on how to handle this. Dr. Phil says that people need to hit rock bottom before they are truly ready to clean themselves off (and Dr. Phil is ALWAYS right!! ;-) ) My mother doesnt feel the same and wants to help him out. (Which Dr. Phil would call enableing!!). What would you do in this situation? Sit back? Intervene?