This question might have multiple layers to it.
Background
I have been taking photos of people for the past two years. These people of course have verbaly consented to this. You could call them amateur models.
For the past year, I have been told by various people that I should release some of the photographs, as they are really good.
Most models are adults, but some are minors (17 yrs old). There is no nudity involved, naturally.
My Plan
To promote my pictures locally, I intend to print some of them on Postcards. As I have resolved the technical issues and am about to sign a contract with a professional printing service, the legal issues have come to bugger me.
I don't intend to earn a lot of money with these postcards. But I do want to cover my expenses by selling them for a minor amount of money.
I don't know if that already qualifies as a commercial endevour.
All models have given me verbal consent on printing their pictures.
I did however read that I should let them sign a release form. But only if I intend to sell the postcards in a comercial fashion.
Also I've read that for my underage models I need a written consent of their parents.
The Question
Do I need written consent from the adult models? Even if I don't intend to make money of their pictures.
And do I need written consent from the parents of my underage models, aswell?
Post Script: I currently live in Germany.
Edit:
I guess the relevant portion of the question is:
Does selling the postcards for an amount of moeny that covers their production cost constitute making money?