Optional additional input fields in a classified ad post process
New here - so hello to everyone!
I am sitting with some considerations around rearranging/redoing a form for posting an ad on a classified site. My issues being that depending on category, some of the forms carry MANY input fields. Not all of them are required fields, but most likely I will not be allowed to remove the optional ones. But to still make the form shorter and easier for the user to obtain an overview for (especially on mobile) - I am so far thinking about two options:
Create the function where user is invited to +add additional information fields depending on his/hers needs (from predefined list) which then will add the wanted input fields to the form. Pro: Sort of give the user the power to "create" according to his/her needs. Con: Does require a few extra interactions from the user.
Create a tab/fold-out "+additional information" - so the form stays fairly short at first glance and then user can choose to open/unfold further input fields. Pro: Noise/friction is hidden - form not overwhelming. Con: Risk of hiding the fields too much. As much as they are not required - the fields carry information which will improve the advert quality (something that really is needed in general for the site from the "buyer" users.)
Do you guys have other suggestions? What do you think? Keep in mind that it needs to be mobile friendly - and I might even have to get it to work on Opera Mini in Extreme Mode.
Thanks so much in advance!!!