I disagree with selling joints. I would never buy one - I'm too afraid of ending up with schwag or oregano. BUT, if it's only your friends, that shouldn't matter if they trust you.

If you're going to expand, you're going to need a scale, because people DO weigh their sacks. Growing up, I had a friend who insisted on weighing every dub (gram), and if it was skimpy, he'd complain.