How Many Guns to Own For Survival

Consider The Ammunition First

I'd consider four types if you want to limit your purchasing.  You can buy the weapons that fill out this list.

Four Rounds to Consider:  .22, 9mm, 5.56, 12 or 20 Gauge.

.22 in rifle and pisol

9mm in pistol and carbine/rifle

5.56 in the obvious weapon, an AR-15 style weapon.

12 or 20 gauge in a pump shotgun

What ammunition type to get first. 9mm

What weapon to get first.
If I could only buy one weapon based on one caliber I'd go for a 9mm premium quality pistol. 

Reasoning: 

I would consider going with 9mm just to have a relatively low cost practice round that can fill all the categories you need if you find yourself limited by finances and need to stick to one caliber and two weapons, a handgun and a rifle.   You could get a 9mm carbine as the follow up weapon and stay with those two and only be limited to range  Sure, it's not for hunting or long range shooting but within the boundaries of self defense it is a great choice.  You can load up on that round in FMJ for practice and JHP for actual use.

Handgun Choice

If you want a gun recommendation try the Glock 19, the most popular of the Glock line and probably one of the most popular 9mm pistols ever built.  You can buy a used one and still rely on it.  I've purchased numerous used Glock pistols over the years and never had a bad one.  Of course, you can always just spend the extra dollars for a new one.

Work on your handgun skills.  You can always practice your rifle skills with a pellet rifle.  That might be the cheapest way to improve your long gun skills until you choose to pony up for the bucks to get the rifle, buy the ammo, and find a range to go to in order to practice it.

Carbine/Rifle Choice

The Kel-Tec Sub2000 is a great short range carbine with the added advantage that the price is around $400 and if you can buy one that uses the same Glock 9mm magazines that fit your pistol.  One thing to note is that you need the Glock 17 magazines and not the shorter 9mm Glock 19 magazine that holds 15 rounds.  Other than that you have successfully avoided a cost and logistics issue by having two weapon types that use the same Glock magazine.  

Your other options are the Beretta CX4 carbine at more than $750 or Hi-Point 995 carbine.  The Hi-Point is a very robust weapon and is reliable though heavy and less than $350 though the magazines aren't interchangeable with the Glock and are standard 10 rounds, though higher capacity versions may become available.

Ballistic Realities

The maximum effective range on a 9mm as an antipersonnel round is close to 150 yards though many would say 100 yards.  You'll have close to 200 ft lbs of energy left at 150 yards with a bullet drop of close to 3 feet.  It is workable for  close range small game but your main concern is self defense and anti-personnel.  Sure you won't outdistance a 5.56 or greater but your protection zone within 100 yards is solved.  Anything beyond that is realistically something you won't face in most instances and especially until the SHTF.

Bottom Line:  Get something and train with it.