If you want to make some real money in Skyrim, you're going to have to earn it. By earning it, I mean risking your life and limb in caves, grottos and forts throughout the land. That's because weapons and armor are pretty much the most valuable items you can get your hands on. The problem is that most of the good stuff doesn't just willingly fall off of seasoned bandits and wizards, nor can it be found just lying around.
Thanks to your annoyingly realistic weight limit, you’ll need to be selective about what you pick up. Jewelry and staffs are the bomb because they are low weight, high worth, whereas something like an iron suit of armor is low worth, high weight. If you have a housecarl or mercenary cruising around with you, use them as your mule so you don’t have to carry so much. They won’t care. Your housecarls are especially excited to help you. Except for Lydia, that sarcastic wench.
When you want to take your arms dealing to the next level, bring your wares to an enchanting table and amp up the jewelry, weapons, and armor. Sell each item to merchants according to their type for the most payout.