If I want user to create a main content which can be able to add multiple sub-content for example I wanna do apartment renting website. User have to create the apartment details which contain these fields; Title, Description, Address, Facilities etc. As 1 apartment usually have multiple different units, user have to add their available units in the apartment node which contain fields; Unit title, room size, bedroom, bathroom, price. And they can add many units as they want. The question is what module should I use? Can I use Organic Group module or something simpler then that?
I'm new for Drupal, learn by myself from scratch, anyone please point me the direction.