7.62x39 will remain cheap pretty much forever. Wolf is a bad ammo brand that you should avoid; Golden Tiger or similar authentic slavshit rounds are usually great. The SKS is an exceptional & low-cost rifle (average price is $400) that will do anything you need a gun to accomplish. There's plenty of polymer options offered up by companies such as PSA but if you want the swiss army knife of guns, SKS is your best bet. Sadly the AK platform is too well-known to be cheap anymore. Never buy any gun made in Turkey. Also be aware that this is a big Soviet boolet & should not be used for home defense, you will miss, fire through a wall and kill someone's dog 2 blocks away.
Fudd hunting rounds can be expensive but they have a secret buff that prevents them from ever being banned by the federal government since Joe Biden isn't afraid of them. Do not underestimate the power of buying some dead grandparent's 30-30. These also aren't made for home defense.
Shotgun shells will always be cheap (because you can make them) and they are viable for home defense since pellets tend not to over-penetrate through walls while penetrating reliably through humans. Used shotguns thrown away by police are dime-a-dozen so anything constructed in the United States & not visibly rusted will suit your purposes for about $200 - 300. The Ithaca 37 is one of the finest firearms ever made but beware pussified variants that take measures to prevent slamfire.
When it comes to pistols do not trust your life to meme rounds like 9mm, .22 or 9mm. You should not entrust your life to 9mm. If you are shopping for personal protection, it's important to look for specific details such as ensuring it is not chambered in 9mm. Tyrone will take another dab of PCP & bath salts like a potion in World of Warcraft upon being hit with 9mm & he will not be dead. If you buy anyway 9mm I will tell you to use it on yourself knowing full well you will just wake up in the hospital a few hours later. Instead spring for .45 ACP or 10mm. There are plenty of Czech or Sig Sauer options that won't exceed $600.
I never recommend black polymer hunks of crap chambered in glorified varmint rounds like 5.56 but I understand some people like the look & find such rounds easier to fire. The aftermarket on these items is also incredible because scared liberals will buy one, keep it pristine in a drawer, remember guns are scary later & sell them. These are also cheap but they are cheap for a reason. You should really scroll up & look at the SKS, or if you're a tacticool retard consider FN SCAR platform (which is only cheap relative to the standard regarding big-boy modular rifles.)
