I know there is a spell to light an arrow.
But what if I just want to buy/craft some arrows with a sort of "torch" end that I can light and fire? I assume the damage from the arrow would be less, or its range less, but it would come with extra burning damage.
I can't find anything in the rule books for it.
Best Answer
There aren't any.
(At least not in the core Players Handbook or Dungeon Masters' Guide)
You will have to work with your GM (or players) to figure out how to adjudicate nonmagical flaming arrows.
There are, however, rules for using other sorts of fire as a weapon.
(Note: Improvised weapons suffer a -4 penalty to hit)
We can also consider the historical use of actual flaming arrows.
There is a well researched and easy to digest wikipedia article on the subject.
When flaming arrows were used, they were created by soaking a cloth in some kind of flammable material, and wrapping it around the head (like a torch). The result is not only heavier than an arrow, and blunted, but also padded, and utterly ineffective against things that don't burn well, like people. Fire weaponry was primarily used to destroy crop-fields, tents, thatch-roofed buildings, and other flammable material possessions. They were a strategic weapon, not a combat one.
Taken together, I would adjudicate flaming arrows as being equivalent to ranged torches.
And add specific rules for setting objects on fire, since that's what I expect them to be used for.
A flaming arrow suffers a -4 penalty to hit, has a 30' range increment, and deals damage equal to a gauntlet of its size category, plus a single point of fire damage. It also can ignite flammable objects where it lands, if not removed or extinguished. Oil and similar substances ignite instantly, dry grass, thatch, or cloth ignites after one round, and wood ignites after 1d4 rounds. Removing or extinguishing a flaming arrow before it ignites its target is a move action ("pick up an item") which provokes an attack of opportunity.
This is, however, homebrew, and not RAW.