만날 사람 없네 I don't have anyone who I will meet
만날 사람 means "a person who I will meet"
만날 >> 만나(다) + 을
만나다 means "to meet"
을 is future modifier suffix.
만나는 사람 means "a person who I meet" present
만난 사람 means "a person who I met" past
A verb can be a modifier with modifier suffix 은,는,을.
Modifier form have tense like as verb by adding tense ending.
어제 사과를 먹었다(I ate an apple yesterday)
어제 먹은 사과(an apple which I ate yesterday)
먹은 is 과거 관형사형(past modifier form) of 먹다
지금 사과를 먹는다(I eat an apple now)
지금 먹는 사과(an apple which I eat now)
먹는 is 현재 관형사형(present modifier form) of 먹다
내일 사과를 먹을 것이다(I will eat an apple tomorrow)
내일 먹을 사과(an apple which I will eat tomorrow)
먹을 is 미래 관형사형(future modifier form) of 먹다