The first is correct but not natural.
The second is even more unnatural.
The third is incorrect.
Student or Learner
They are looking for an apartment “in which to live”.
Jack is a nice person “with whom to work”.
I will marry the man “who to help my father”.
-Are the three sentences correct?
The first two are grammatically correct. More typical usage would be "They are looking for an apartment to live in" and "Jack is a nice person to work with." Some teachers still teach their students not to end sentences with prepositions but there's nothing wrong with the practice.
I am not a teacher.