If I wanted to open a shop towards the end of the Roman Empire, how would I do that?

by Telochi

Where would I get my supply from?

Would I have to pay any taxes, or abide by any regulations?

freeogy

Just a note, if you want a more accurate answer you might want to specify a place within the Roman Empire and which time you mean. That is to say that an Iberian might have a different experience in 425 CE Tarraco than somebody looking to open up shop in 525 CE Antioch.