Just did a quick look on Cars.com..... listed 12 used M3 sedans below $50k. Most had 20,000+ miles.
BMW website shows 1 sedan under $50k.
Looks like you have some research and investigation to do. Best of luck.
| 2011 M3 Sedan | Le Mans Blue | M-DCT | ZC2 | ZCP | ZP3 | Moonroof | Enhanced Premium Sound | Dinan exhaust | Dinan software | Dinan pulley | Dinan intake | Dinan pedals | Bimmian LED interior | Lux H8 V3 | WeissLicht PY24W LED | 20% tint | IND reflectors | IND front grills | IND key hole cover | IND hood vents | IND M5 mirror covers | Reus Systems audio | Verstraβe shifter paddles | BBS LM 20x9 et 15 and 20x10.5 et 15 | Hankook Ventus V12 255/30/20 and 295/25/20 | Red BBS Racing lug nut kit | H&R Sport springs |