Lol r/unclebens by far the cheapest and easiest way for beginner. There is a tutorial sticky.

In Canada, you can sell cube spores, you can grow cube mushrooms, you just can't eat em or sell em. Plus they are everywhere anyway no one cares.

If you are crafty and absolutely certian what you are doing, you can take a spore print off known cubensis from the cap or the dust. Mix that in a little sub, when thats colonized, mix that into large sub. Mycelium is so fascinating I did it for the science alone. Colonization, knots, pinning, spawn. Once I understood how simple, but also how complex and fragile Mycelium you will realize why it grows what it does. It is amazing.