Other folks are suggesting 8 track reel to reel--I suggest 4 track. Half inch, 15 inches per second. That will get you some good tape sound.
If you want lo-fi, get a cheap cassette deck, not a 4-track cassette.
Go to ebay, look at Tascam, Sony, MCI, Scully, TEAC see what's around. Should be cheap. Get a 3-head machine NOT 2 heads, and learn how to align it. 2-head machines are much harder to align.
And don't just record guitars with it--think about drums too.
I'm a cheapskate dude recording friends in my house. I did 4 track cassette in the 80s, reel to reel in the 90s, and I'm using a computer in the 00s. I decided that cheap digital sounds better than cheap analog, and I wasan't doing the maintenance well enough (aligning a 1/2" 16 track 2 head machine is a pain in the ass) to keep it. Besides, I can fix computer problems more easily than mechanical/electronic problems.
But if you have the commitment to go for the 1/2 inch 3-head four track thing, it will sound good--not like cheap analog.