[RPG] Are there requirements for crafting magic items

There are two official optional rulesets for crafting

Both are optional and require that you work with your DM as to if they're an option and how they'd work. In either place that these rules appear, they are optional variants to the base rules.

Dungeon Master's Guide

The first official optional rules released appear in the Dungeon Master's Guide in chapter 6 as part of the "Downtime Activities" section:

Crafting a Magic Item

Magic items are the DM’s purview, so you decide how they fall into the party’s possession. As an option, you can allow player characters to craft magic items.

Within these rules, there are the following requirements:

• a formula that describes the construction of the item
• the character must also be a spellcaster with spell slots and must be able to cast any spells that the item can produce (and expends the relevant spell cost each day during crafting)
• the character must meet a level minimum determined by the item’s rarity
• a required gold and time cost to craft the item during downtime (consumable cost half as much as other magic items)

\begin{array}{c|c|c} \text{Rarity}&\text{Cost}&\text{Minimum Level}\\ \hline \text{Common}&\text{100 gp}&\text{3}\\ \text{Uncommon}&\text{500 gp}&\text{3}\\ \text{Rare}&\text{5,000 gp}&\text{6}\\ \text{Very Rare}&\text{50,000 gp}&\text{11}\\ \text{Legendary}&\text{500,000 gp}&\text{17}\\ \end{array}

Xanathar's Guide to Everything

An alternative ruleset is part of the optional variant to downtime as a whole (and one I personally think is more fleshed out) that appears in the supplement Xanathar's Guide to Everything in the "Downtime Revisited" section of chapter 2:

Crafting Magic Items. Creating a magic item requires more than just time, effort, and materials. It is a long-term process that involves one or more adventures to track down rare materials and the lore needed to create the item.

Within these rules, there are the following requirements:

• a formula for a magic item in order to create it
• an exotic material to complete it. This material can range from the skin of a yeti to a vial of water taken from a whirlpool on the Elemental Plane of Water. Finding that material should take place as part of an adventure. (the suggested challenge rating of the creature to face, though not necessarily harvest the material from, appears in the table below)
• whatever tool proficiency is appropriate, as for crafting a nonmagical object, or proficiency in the Arcana skill.
• a required gold and time cost to craft the item during downtime (consumable cost half as much as other magic items). Do note that downtime rules as a whole are revised when using the Xanathar's Guide to Everything rules

\begin{array}{c|c|c|c} \text{Rarity}&\text{Challenge Rating}&\text{Time}&\text{Cost}\\ \hline \text{Common}&\text{1-3}&\text{1 workweek}&\text{50 gp}\\ \text{Uncommon}&\text{4-8}&\text{2 workweeks}&\text{200 gp}\\ \text{Rare}&\text{9-12}&\text{10 workweeks}&\text{2,000 gp}\\ \text{Very Rare}&\text{13-18}&\text{25 workweeks}&\text{20,000 gp}\\ \text{Legendary}&\text{19+}&\text{50 workweeks}&\text{100,000 gp}\\ \end{array}