Ive been thinking about whether as a dm I should let my players buy magic items. What do you think?

It's almost always a good thing to let the players have access to common magic consumables; healing potions, magic scrolls, and the like.

Having a shop where they could get some un/common weapons and armor I tend to leave that to the large cities. I feel that the small hamlets, villages, and outposts aren't going to have access to them easily and the ones they do have will be very important to that location. 

I am also the type of DM who feels that magical items should hold some sort of weight to them, they have an intrinsic value over a monetary. My players got their first magic items after winning a major series of challenges in a tournament. They haven't been able to purchase any magical gear because their renown isn't enough for the major cities to trust selling them yet. One player is trying to see about getting gear enchanted, again they are in a bad spot where the cost is absurdly high, again due to their renown. As they become more and more known as heroes of the land, these goods and services become easier to come by and less expensive. 

I agree, but recently my players have bugged me to be able to buy rare-legendary magic items, what's your advice on that?

"Rare" or "Legendary" is the precursor to a fantastic voyage into the catacombs that were just opened in last summer's floods....Give them the first half of the rare/legendary/artifact item, then have them quest to complete it.

You can have the odd rare magical item in a shop, but the shop keep is going to know what they're selling, know it's value, and know to get as much money out of the would be buyer as possible. 

As an aside, if you decide to go the black market route, don't forget the cursed items and the shady salesman. I have a city in my world where the sale of magic items is prohibited, the black market thrives, and the one merchant has really good prices...however there's a 30% chance you'll get yourself a cursed item instead of that Ring of Protection +1 you thought you purchased.

I would suggest maybe at most allow them to purchase rare magic items, depending on what level the characters are. Of course, an appropriate expensive price should be tacked on, and perhaps let the players know that items like these are indeed rare through the shopkeeper selling the items. Perhaps making a table of what magic items a shopkeep has on them and whether or not the items in question have already been purchased could be a good idea.

If access to Xanathar's Guide is available, take a look at the table for possible complications in purchasing magic items and decide whether or not to use it.

Anything above rare that is magic I personally believe should only ever be rewarded to players that have gone through some ordeal to obtain the item, thus I personally believe that magic items of that caliber should never be able to be found in a shop.

Curse of Strahd gives a good example in having three or four legendary magic items able to be obtained by the players, but each one involves going to a dangerous location and then needing to seek and find said item by carefully searching through the area, and even then, they are in very specific spots.

That is my two cents about the idea.

I have seen the table in my copy of Xanathars guide, and I get your advice on the legendarys, but what If there is a specific item my players want and my modules don't have it because they're  practically all 1e.

First you look up the item on the interwebs, get a feel for what it is and how it will affect your game going forward if they were to have it now.

If it's something you think would be fine in your game: make them quest for it. (Explain something along the lines of Excalibur..Arthur didn't just walk into a general goods store and buy it, he had to prove his worth by pulling the sword from the stone.)

Let's say, for the sake of argument, that they want to purchase the Holy Avenger. Your group goes to the local armory, the clerk says that has never been through the store, but here's an amazing +2 greatsword that he just got in, and I'll even give you a discount. When the players refuse he points them toward the weaponsmith. They then go to the weaponsmith, he says that is beyond his ability to make, maybe the church has some information. They go to the church, the Abbot tells them that he can help them obtain it, but it's not so simple as to gather some metal and cast a couple spells, it's something that must be earned. The abbot gives them a holy relic, a small disc with the emblem of the paladin's deity on it, and they are charged with finding star metal, the Dwarves or Gnomes may be able to help with that. Now your players are off on a journey, you've given an in game mechanic/metric for why the item isn't available and you've given them a way to acquire the weapon that they want.

Never let the players bully/pressure you into something. Be you a new DM, or a veteran, you are in charge of all the wealth, rewards, and challenges the players receive.

Thankyou, I shall create a new adventure for them. 

I have to agree with the others. You're not going to walk into a shop a pick up a legendary anything. I suppose you can have a campaign with magic dripping out of everything, that would be your choice.

I think it's totally up to the tone of your game, and the setting you're in. How magic is your setting?

My current campaign totally goes the other way: all magic items are an artistic creation of the mage/craftsman who made them. There is no such thing as a generic +1 sword, but there are named swords of great renown. Typically they're better than a simple +1 weapon, however.

In my setting, players can't walk into a shop and buy magic anything. Magic items are things to be quested for, and prized possessions of their owners.

You can take Xanth as an example of magic everywhere.

I find it depends on the kind of game you run. If it is really highest of the high magic settings then magical items would be a lot easier to have, sell or trade. They might even be the currency of your setting. If you play mid to lower end of the magical spectrum it'll be a lot more difficult to get your hands on magical items. There might be an enchanter/mage somewhere that can make uncommon and the occasional rare magic item. If you use the crafting time per core books then its understandable as well. It takes quite some time to create magical items. Meaning that everything above rare quality is very hard to come by...****y from old blocked off/forgotten tombs and areas in the world.

Or perhaps that some very rich noble is willing to organize an auction for 1 or 2 such legendary items with a few wondrous items at one point. Which can include other parties trying to steal the items before the auction. Or some intrigue turning this into a side quest of its own.

In my current low-mid fantasy setting the shops have a small selection of standard magical items. Most everything else is found by exploring, dungeoen delving, adventuring and what not. If they want to commission an item from an enchanter its going to take a week or so to make. Meaning they can go do something else and come back later to pick it up...if they didn't forget.

@DMThac0
Cursed items can be funny. In a campaign that I'm a player, the DM dangled a plate armor in front of our faces. Its price was only 1000gp. Cleric broke in, stole the item, put it on. It turned into a metal bikini he can't take off. Any item he puts on shifts to match the bikini. lots of negative bonuses as well. I mean no one would be intimidated seeing him in a bikini.

they can roll for arcana, religion, or history to get some lore that starts them on a quest.

didn't the knight Huma have a magic lance?low dc history check. 

wasn't it magic? higher DC arcana...

where would he be buried?...  very high dc religion check that would require traveling to the ruined temple of Paladine to even attempt.

Quote from Giblix >>

 

@DMThac0
Cursed items can be funny. In a campaign that I'm a player, the DM dangled a plate armor in front of our faces. Its price was only 1000gp. Cleric broke in, stole the item, put it on. It turned into a metal bikini he can't take off. Any item he puts on shifts to match the bikini. lots of negative bonuses as well. I mean no one would be intimidated seeing him in a bikini.

That right there, that's a cursed item used to its best effect. I don't mind the Necklace of Choking popping up, or a Bag of Devouring, however a mechanic like that really sets a tone of fear. If you want to have the players wonder if their magic items are legitimate or not, using something like this may be a lot more fun.

What I (plan to) do is roll on the treasure tables in DMG for shops in small towns as the "items in the back."

Large towns might have dedicated magic shops with common and uncommon items readily available and roll for rare "items in the back."

If they want a specific item, follow the buying magic item downtime in XGE.

Consider the rarity of such items when selling them. Rare and very rare items might be pieces in a noble's collection or a museum. Legendary items might be national treasures. Artifacts are either unheard of or the stuff of legend.

As such, remember to raise prices appropriately. Common items are 50-100gp, uncommon are 100-500gp, and it only goes up from there (see DMG and XGE).

In the case of weapons and armor, remember to add the cost to their normal costs. And consumables are half price.

These are the rules I go by anyway.