I've had two potential buyers just about to meet me flake out once I mentioned that I would check their bills to make sure they weren't counterfeits. It's only checking them off with a marker one by one, is that too much to ask? Is it normal for sellers to check the bills or not? It's my first time using Craigslist just to sell an extra iPhone 4 and my tactics don't seem to work. I'm asking to meet somewhere crowded, Starbucks was my preferred location. Do you guys have any advice on how to handle potential buyers?