How many Mezuzot?

If I just have a Mezuza on my front door do I need mezuzahs for every door in my apartment?

Absolutely.

But you should be aware that if the room is less than 8 x 8 feet it does not require a mezuzah. This measurement is based on a rental, which I assume is the setup in an apartment. If on the other hand you own the apartment the room size only needs to be 6 x 6.

Additionally, Its worthwhile to note, that if the front door does not open to a room of adequate size (as mentioned above) you would not affix a mezuzah to the front door either.

Lastly there is a misconception that the front door in some way is more pertinent than any other door in the house. This is a mistake.

Awesome thank you so much that helped me out tremendously!

Interesting. If your front opens into a narrow hallway, you do not attach the mezuzah to the front door. Is it improper to thus have a mezuzah on the front door? I mean, should people who have them, remove them? Thanks.

You asked.

If your front opens into a narrow hallway, you do not attach the mezuzah to the front door.

Correct.

Is it improper to thus have a mezuzah on the front door? I mean, should people who have them, remove them?

Good question.
Let’s put it this way. At present that mezuzah is serving no purpose. Sitting in your drawer it also serves no purpose. In the event that you have a need for the mezuzah, (example. New doorway in the house, a friend wants to buy off you or the like) then by all means remove it and put it to use.

Thanks!

My mom owns an apt building. Does she need to have a mezuzah on each apt doorway if she rents the apartments? Initially, she put mezuzot in all the apts but they were removed by tenants long ago. Is she required to put up mezuzot between tenants?

She only needs to put a mezuzah on a dwelling (a place she actually lives in) or a room that is secondary to the dwelling even though she does not live there. For example a shed or garage whose usage compliments the house.
In a case of an apartment building that she does not live in, she should not put up any mezuzos. The requirement falls fully on the Jewish tenant.

Thank you