As I said....just how ghetto are you willing to go (obviously in an aerospace engineering context...)?
3D printing isn't as rapid as say punching out shapes with a press or vac forming plastics and some aluminiums are far more available in useful shapes than just about all aerospace grades.
When I was designing a research test I wanted to purchase some L shaped extrusion material in a common aerospace grade. Not possible. Had to buy blocks and machine away the vast majority.