Belethor is a Breton merchant that owns Belethor's General Goods in Whiterun. He's a general merchant and will buy anything (as long as the item isn't quest essential) and sell general goods. He jokes that "Everything's for sale my friend. Everything. If I had a sister I'd sell her in a second." and "I'd even buy one of your relatives, if you're looking to sell. Ha ha ha ha. That's a little joke."
He lives the life of a busy merchant, spending most of his time running his store. He will open up at 8 AM and the shop will stay open for twelve hours. After closing the store, he will go for a walk around Whiterun for four hours. He first heads to the main gate of Whiterun and turns right at the guard barracks to head north up the steps and eventually reach the Gildergreen after passing Amren's House and House Gray-Mane. From the Gildergreen, he will head down the steps into the Plains District and back to where he started. This route will be repeated until midnight, where he will return back to Belethor's General Goods and sleep until 8 AM to open the shop next day.
Belethor wears a set of farm clothes, a pair of boots and a pair of gloves. He carries an iron dagger, the key to his store and some common loot and gold. He will often give sarcastic responses to questions asked. If the player asks why he came to Skryim, he will sarcastically answer "Isn't it obvious? Why, the wonderful weather and hospitable people, of course! Not to mention my great fondness for dragons and petty political power struggles Ah, but without a doubt, the most compelling feature of this frozen wasteland is the volley of inane questions leveled at me on a regular basis."
If asked about how his business is going, he will give an answer that isn't sarcastic: "Interesting, to say the least. What with all that's been going on. On the one hand, supplies are harder to come by, since fewer traders are traveling the roads these days. But on the other, the scarcity of supplies has led to some, well, 'elevated' prices. All that matters is that I have what you need. And it's worth every septim." Although, after the Stormcloak siege on Whiterun, he will instead reply with sarcasm saying: "Oh no, not at all. I simply locked the doors, hid beneath my counter and prayed to the Divines that my life would be spared and my shop wouldn't burn to the ground. But other than that, everything was business as usual. Now, do you have any other painfully obvious things to say?"