Hey guys so i am new to the world of 3D printing and my friend currently uses a little 3D printing pen and make some cool things and she sells them but i was wondering how well can i do as a small 1 man business ? will i see a return on my initial investment ?, also which is better the 3D pen or a proper 3D desktop printer

so for example if i made little things like keyrings, tiny ornaments and other things it just worry's me it might not sell well