You *can* use a 4x at 25 yards, but you're not going to be very fast on target.
I'm pretty comfortable using 3x and lower magnification at fast and close shooting by leaving both eyes open and just point shooting for the stuff that is really really close, but to me 4x crosses over to being just a little too much magnification for getting on targets quickly.
I know you're looking for a scope, but in your price range you probably wont find anything of high quality. You need a mount, which is a bare minimum of $30 for the lower end mounts, then a scope that will be 1 or 2 variable power... Not saying they don't exist, but I have never seen a tactical scope that I would trust to withstand AK-47 recoil for $70 or less.
Now, you say you want to hunt with it, but what else are you planning on using this rifle for? At what ranges and for what game are you planning on hunting?
I am biased towards iron sights because that is what I run, but let me explain my reasoning.
I have an SKS with tech sights (rear mounted ghost ring), and it can hold 10 shot groups inside a 10" target at 200 yards all day, any day, with "cold bore" groups doing even better. That means it maintains deer hunting accuracy well past the effective range that you could hunt deer with the 7.62x39mm round (I would only trust a clean deer kill from x39 inside 150 yards or so, using SP ammo).
So, assuming that the AK will have similar accuracy with tech sights (which I will be testing this weekend with a WASR), there is really no reason to want optics if you are going to use it as a brush gun (which is all the x39 ballistics will allow when you're talking about a clean deer kill).
Plus, for shooting the paper bad guys, you'll find that quality iron sights to be more than enough for hitting torso sized targets at 200 and 300 yard ranges (provided you're a decent shot), which are the max range distances we have on long island; and certainly well beyond the reasonable realm of defense preparedness... Not to mention, with factory loaded x39, optics aren't going to help you a whole lot beyond 350 yards.