Paladin intended to multi-class as a Draconic Sorceror Query

[Hopeless]

I've been looking at 5e for a while, but I need some advise as I'm wondering if I should be considering picking up more books than the Core Rule books and the starter set.

The idea for the character is a half elven male Paladin whose considered a former soldier and mercenary whose hide his past after his father died defending him from a group of Harper agents sent to kill him after a member of their order divined him a future threat to their organisation.

His paladinnic status has been well hidden and using quite a few alternate identities he's tried to rebuild his life after early efforts to track down his father's murderers led nowhere and he had been briefly married with a child of his own to consider.

This is how he stands at first level, the idea if I ever get to run this character is that he'll proceed to 3rd level as a Paladin before multi-classing to Sorceror of the Draconic Heritage (specifically Silver).

Been watching Force Grey Giant Hunters so it made me more curious about how to handle such a character.

Any advise would be appreciated!

Equipment: Thinking of replacing the Chain Mail with a Chain Shirt, part of his back story would lead him to follow in his father's footsteps by investigating some of his father's notes specifically tracking the sword of a long deceased Bulwark of the now long dead faith of Helm named "Future's Passing".

A few years ago back in 3.0 I ran a Cleric who purchased a +1 Bastard Sword and had it enhanced with the Sure Striking talent.

Now I may have run and played 4e, 3e, etc, but I have yet to dabble that far with 5e so apologies if I'm making some mistakes here but if the dm was reasonable I was planning on acquiring that sword to function as an alternate form of familiar.

Now this might not be possible under 5e rules but I figured finding that out now would be better than when I eventually get that far!

[famousringo]

I'm not aware of any way by RAW to take a sword as a familiar. In fact, the simple act of purchasing a magic sword is kind of discouraged in 5E. That's not to say that your DM couldn't let you do any of this, but it's not exactly core rules.

The closest thing to a sword familiar I can think of is the 3rd level feature of Eldritch Knights or Blade Pact Warlocks, which allows you to bond with a weapon or two and conjure it with a bonus action. Perhaps you should consider a paladin/warlock multiclass instead. Oath of Ancients paladin blends nicely with a fey warlock from an RP perspective.

Since you're only taking paladin to 3, you're missing out on Extra Attack. This isn't the end of the world, since you'll have lots of spell slots you can use to Smite from your caster class, but with your caster class you should look at getting either Booming Blade or Greenflame Blade from the Sword Coast Adventure Guide.

And if you're using a "mundane" sword that comes at your command and splashes magic fire everywhere, well, it doesn't seem so mundane anymore, does it?

[Arkhios]

NOTE: Magic items are not yours to freely purchase unless your DM has decided that the campaign has an active magic item market or something. By default, though, magic items are encouraged to remain as rare things.

Well, while a weapon can't exactly be a familiar, it's certainly possible to acquire a sentient magic item (most of which are weapons).
If that's what you could work with, talk with your DM about it. It might be a personal quest for your character to find this "Future's Passing", which could indeed be a sentient sword. (Sentient Magic item rules are found in DMG pg. 214 forward).

A sentient item can be treated as an ally, in many ways like a familiar, while they don't necessarily possess same capabilities as a familiar.

If that's too elaborate and/or fancy for your tastes, it could well be a seemingly mundane weapon with maybe a Minor Quirk (DMG pg. 142)

[Daishain]

One of the more powerful first level features of the Draconic Sorcerer in this edition is the natural armor (perma 13+dex). However, it does not stack with standard armor like chainmail. Unless strength is a core concept of the character, I am inclined to suggest going for a dexterity build. That character, with a Rapier, 20 dex, a shield, and no other bonuses counted, deals respectable damage while protected by an AC of 20, with none of the drawbacks a Full Plate+shield character incurs getting to the same AC.

In regards to the sword familiar, as others have mentioned, blade pact warlocks and eldritch knights have the closest RAW abilities to that theme. But in both cases that mostly just boils down to it being tough to keep the weapon from the character.

If that's not enough, you need to talk to your DM for some homebrew. If it was my campaign, AND said campaign was relatively high power/high magic such that all involved characters were getting at minimum the chance at something special, I might be inclined to brew up an intelligent legacy weapon with abilities not dissimilar to that of a familiar. But that's me, your DM may not be much for wandering away from established material.