Depends on the profession. Some are cheap to level like alchemy and disassembly, while others like enchanting have high costs.
Alchemy produces consumable potions, from HP/MP ones to stat boosting ones like Str/Int ones. At higher levels, you can produce HP/MP potions that heal more than Master potions that drop in higher level dungeons, and other highly useful ones like Sacred Blessing, which auto revives you when you die.
Materials are easy to get - just extract every purple/rare item you get in the extractor you'll have from crafting.
Animator produces APCs that assist you in battle. Most are actually not that useful, so the profession won't be that profitable except for a select few high level APCs, like the FBrawler APC, Sewer Princess Faris who uses Junk Spin to stun, and the FNen APC, Number 28 who spams Nen Guard. Also, there is an NPC shop doll you can craft to merchant cash shop or other items in town.
Materials needed include Protein Oils, which are made by Alchemists, and Animate Spirits, which are profession mats obtained through using the profession's extractor.
Disassember... well, disassembles equipments, much like Loton does (for reference, his grinder is about equal to a lv4 disassembler). Leveling one doesn't take much other than throwing equipment in your disassember and repairing it when it runs out of uses. Cursed items can only be disassembled at a high level disassmbler. You can charge for usage much like the many others you see in town, but most tend not to put a fee on their grinder unless their profession is lv7 or higher. You'll be competing against others in town, so profits will be limited until at near max level (lv7-9). However, having a disassembler near dungeon entry areas is more convenient than walking to Loton all the time. This along with Alchemy are the best professions for the self-sufficient player.
Enchanting uses Monster Cards that drop in dungeons to imbue your equipment with additional bonuses. Some high end cards have great bonuses, like Admiral Von Beornan which adds +11 fire damage or Agram, which adds Magic Attack Strength. However, most profits regarding the profession are tied to the monster cards, not the actual professional service, leaving Enchanting to be the most expensive and unprofitable profession there is. Each enchant requires 1 monster card, some Mana Solvents (drops in dungeons), and some Low or High Grade Elemental Crystals (lows from disassembling purples/rares, high grades from disassembling uniques/pinks). Because most of the high end enchants desired by endgame players require High Grade Elemental Crystals that can only be obtained from uniques, it's difficult to get the large amount needed to level the profession easily.
So why make would anyone make an Enchanter if it's so unprofitable? Because somebody has to do it. Sometimes you see echo megaphones where people are looking for a lv9 enchanter.