Reimbursed for Support

I have a friend who lived with me for 6 yrs who I financially supported in much the same way a parent does for their child; cost of living, buying clothes, basic needs, pay for things to try to get ahead, etc. After the friend moved out years later he wants to reimburse me back and we agreed to $30,000. He plans to pay me in 3 or 4 installments. He's been approved for SSI. SSI has confirmed he will be getting a certain amount in back pay disbursed in 4 checks so he'll be giving me about $7k-10k in 3 to 4 consecutive months. I was not able to claim him on my taxes during those 6 years because of 2 reasons; first, I did not know I could claim him then second, when I found out I could claim him I tried to do so but someone else had already claimed him on their taxes. 

 

As of current there is no formal or notarized agreement for him to pay me back. Do I need to file tax on this? Whether yes or no do I need need to have something formalized or notarized showing an agreement between the he and I? I would hate to find out that I would have to file and pay taxes on the very money I supported someone who, in return, is reimbursing me back.