It is fairly easy to adapt the 3rd edition rules for Craft and Profession skills to 4th edition. Mostly you just have to adjust the DCs. Below is my adaptation:
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Craft and Profession skills
adapted from 3rd edition Dungeons & Dragons SRD and Iron Heroes
CRAFT (Intelligence)
Craft is actually a number of separate skills. You could have several different Craft skills, each purchased as a separate skill. A Craft skill must focus specifically on creating something. If an endeavor creates nothing, it probably falls under the heading of a Profession skill rather than Craft. When you choose this skill, select a material to work with, such as wood, stone, or metal. You can use your Craft skill to produce anything that is primarily composed of that material.
Check: You can practice your trade and make a decent living, earning about half your check result in gold pieces per week of dedicated work. You know how to use the tools of your trade, perform the craft’s daily tasks, supervise untrained helpers, and handle common problems.
The basic function of the Craft skill, however, is to allow you to make an item from the appropriate material. The skill check’s Difficulty Class depends on the complexity of the item to be created. The DC, your check results, and the price of the item together determine how long it takes to make a particular item. The item’s finished price also dictates the cost of raw materials. Using artisan’s tools in your Craft attempt gives you the best chance of success. If you use improvised tools, make your check with a –2 circumstance penalty. On the other hand, masterwork artisan’s tools provide a +2 circumstance bonus on the skill check.
To determine how much time and money it takes to make an item, follow these steps.
1. Find the item’s price. Put the price into silver pieces (1 gp = 10 sp).
2. Select the appropriate Difficulty Class from the table below.
3. Pay one-third of the item’s price for the cost of raw materials.
4. Make an appropriate Craft check representing one week’s work. If the check succeeds, multiply your check result by
the Difficulty Class. If this result equals the price of the item in silver pieces, then you have completed the item. If the result multiplied by the Difficulty Class doesn’t equal the price, then it represents the progress you’ve made this week. Record the result and make a new Craft check for the next week. Each week, you make more progress until your total reaches the price of the item in silver pieces.
If you fail a check by 4 points or less, you make no progress this week.
If you fail by 5 points or more, you ruin half the raw materials and have to pay half the original raw material cost again.
Progress by the Day: You can make checks by the day instead of by the week. In this case your progress (check result xDC) is in copper pieces instead of silver pieces (1 sp = 10 cp).
Repairing Items: Generally you can repair an item by making skill checks against the same Difficulty Class that it took to make the item in the first place. The cost of repairing an item is one-fifth of the item’s price.
Item Type -- DC
Simple item with no moving parts or complex pieces -- DC 10
Item with moving parts or joints -- DC 16
Intricate item with complex workings -- DC 18
Elegant or rare item -- DC 23
A masterpiece or one-of-a-kind item -- DC 25
Jury-Rigged Items: You can use this skill to create a temporary or crude item. Make a Craft check as described above, but attempt one check per hour to determine your progress in silver pieces. The final item has no cash value, and there is a 10 percent chance per hour of use that it breaks. You cannot jury-rig an item with a market price of more than 10 gp. You must provide raw materials and tools as normal.
Masterwork Items: Craft also allows you to make a masterwork item — an item that conveys a bonus to its user through its exceptional craftsmanship, not through being magical. To craft a masterwork version of an item, use the rules for crafting, above, but increase the DC by 5.
Action: Does not apply. Craft checks are made by the day or week, but see below.
Try Again: Yes, but each time you miss by 5 or more, you ruin half the raw materials and have to pay half the original raw material cost again.
Fast Worker: You may voluntarily add +2 or +5 to the indicated Difficulty Class to craft an item. This increase allows you to create the item more quickly than normal (since you’ll be multiplying this higher DC by your Craft check result to determine progress). You must decide whether to increase the Difficulty Class before you make each weekly or daily check. Use this method when making a Craft check to determine the cash value of your check’s efforts.
PROFESSION (Wisdom or Charisma*; Trained Only)
* Wisdom is the ability score used for most professions, but Charisma is used when the skill is used to lead, entertain, or influence people.
Profession is a actually a number of separate skills. Like Craft, you could have several Profession skills, each purchased as a separate skill. While a Craft skill represents ability in making items, a Profession skill represents aptitude in a vocation requiring a broader range of less specific knowledge. Profession can also cover skills not described elsewhere in the rules.
Check: You can practice your trade and make a decent living, earning about half your Profession check result in gold pieces per week of dedicated work. You know how to use the tools of your trade, how to perform the profession’s daily tasks, how to supervise helpers, and how to handle common problems. Profession checks also determine how well you complete tasks relating to your profession. For example, you would use Profession (sailor) to steer a ship through a patch of icebergs without mishap.
The following professions are examples. DMs may add new ones to account for professions in their own campaign worlds.
-- Animal tender or trainer, apothecary, appraiser, architect, blacksmith, bookbinder, brewer, butcher, butler, cartographer, clerk, composer, cook, dyer, engineer, farmer, fisher, gambler, glazier, governor, healer, herbalist, herder, hunter, innkeeper, lawyer, librarian, lumberjack, merchant, miller, miner, painter, performer, potter, rancher, sailor, sculptor, teamster, weaver.
As you can see, many jobs can be covered with other skills. For example, a hunter or fisherman would use Survival to gather food in the wilderness. Blacksmiths use the Craft skill to create their goods, while an ambassador relies on Diplomacy.
Your DM may allow you to earn a weekly income from a different skill, using the rules described here for Profession.
Action: A single check generally represents a week of work.
Try Again: An attempt to use Profession to earn an income cannot be retried — you are stuck with whatever weekly wage your check result brought you. Another check may be made after a week to determine a new income for the next period of time. An attempt to accomplish some specific task can usually be retried.
Untrained: Untrained laborers and assistants (that is, characters with no training in Profession) earn an average of 1 silver piece per day.
Take 10/20: You cannot take 10 or 20 on Profession checks to earn money, but you can take 10 on checks to complete a specific action or recall a fact related to your profession.
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