Seeing as one can hire guards for PC bases as 'Skilled Hirelings', can I take several veterans with me if I pay them enough?
I am a wizard with low HP, so any guards would be great.
I am playing in an Adventurers League game.
There isn't anything official one way or another about whether hirelings are legal in AL. They are in the PHB so they are part of the rules.
On the other hand, the AL DMG says "Services provided by an NPC are limited to this list." This could mean just the spellcasting services, or it couold mean all services.
Hirelings cost gold.
In AL season 8, gold is in short supply due to the treasure points rules. There are repors on the forums that PCs don't actually get enough gold to do class stuff.
When you get 75gp max per level at tier 1 and revivify costs 300gp, your cleric are not going to be raising many party members. When a fighter needs to be level 12 before they have enough gold for non-magical plate armour, extra gold for hirelings is probably not going to happen.
In home games, hirelings reduce the amount of XP your characters get.
From the DMG, chapter 8:
If the party received substantial assistance from one or more NPCs, count those NPCs as party members when dividing up the XP. (Because the NPCs made the fight easier, individual characters receive fewer XP.)
There is nothing in the AL DMG about how this ties in with the milestone xp system, where xp is earned solely by sitting at the table (a per-hour rate) and achieving story goals.
In all seriousness, the other characters are supposed to be guards. A party should be working to keep foes away from the artillery (sorcerer, warlock, wizard, any archer).
Skilled hirelings can be any skilled service providers.
Skilled hirelings include anyone hired to perform a service that involves a proficiency (including weapon, tool, or skill): a mercenary, artisan, scribe, and so on.
For example Veteran (MM 350):
Veterans are professional fighters that take up arms for pay or to protect something they believe in or value. Their ranks include soldiers retired from long service and warriors who never served anyone but themselves.
But always consider that the Services-Table on page 159 of the PHB shows the minimum wage and that hiring Veterans may be considerably more expensive or otherwise challenging.
The pay shown is a minimum; some expert hirelings require more pay.
Your DM will tell you who or what is available or unavailable in their world and whether hirelings are available to you (AL DM 5).
Remember that experience of combat encounters is split with all characters, including NPCs (DMG 260, also D&D Adventurers League Player's Guide Version 2.0 Elemental Evil, Elemental Evil Edition page 11, and other places).
I have no experience in running AL games so I can't speak much to how hired NPCs would work there. I imagine it wouldn't be much different though.
The most significant effect would be the reduction in XP each party member would gain as hirelings take an equal share of XP.
DMG p. 92:
Any NPC that accompanies the adventurers ... earns a full share of the experience points.
This is true for both AL and non-AL games but I imagine the loss would be more significant for AL players as they move from game to game.
Short answer: yes, page 159 of the PHB details hirelings, examples of skilled vs untrained ones, and costs of employing them. In your case, that would be 2gp per day, at a minimum, if your DM just goes by the table.
Adventurers can pay nonplayer characters to assist them or act on their behalf in a variety of circumstances. Most such hirelings have fairly ordinary skills, while others are masters of a craft or art, and a few are experts with specialized adventuring skills. ... Skilled hirelings include anyone hired to perform a service that involves a proficiency (including weapon, tool, or skill): a mercenary, artisan, scribe, and so on. The pay shown is a minimum; some expert hirelings require more pay.
Slightly longer answer: depends on the DM and your group's playstyle.
Here's how I would handle this as a DM (our group is heavy on role-play and world-building):
First I'd determine if the number and skill level of any likely candidates. Is your current location a quiet backwater? Bustling city? A waypoint on a busy trade route? That would determine the quality and quantity of the available help.
Next I'd look at any competing employers. Are there better paying, safer, or more prestigious jobs available? Different NPCs will have different motivations.
Then I'd take a look at your character's reputation. What sort of adventures have you had, are you surly or charming, what sort of people do you associate with.
There are other factors but you get the idea. All that will help determine who'd be willing to work for you, for how much, how long, and what sort of tasks they will and won't accept.
That may mean the cost may be significantly higher than 2gp/day, their skills may or may not be up to par, and their loyalty and enthusiasm might only go so far.
This way the world feels more 'alive' to the players and brings out the 'C' in 'NPC'.