Cousin Overstaying Welcome?

so my dad died 3 months ago. I found my long lost cousin on fb who apparently been homeless @ 14. my grandparents put him out. hes a troubled kid and his moms on drugs & got kids taken (gma has custody) & no dad. well he lives in nj i live in philly & he works in philly. so i started to invite him over after work because he works overnight and cant get to nj @5 am sometimes. so he would come sleep over (spare bedroom) and leave. well now hes been here over a week. & i had company over. he was trynna crash on my couch and i told him he had to sleep upstairs. he got a little cocky with me. so next morn. thanksgiving... he is GONE. & left a note with $40 ... i felt bad and called him and invited him back over because it was thanksgiving. but now its the next morning & i dont want him staying over again. idk what to tell him or how ?! i wanna set boundaries but like what do i even say. this is a hard spot.. he is 18