THE ORIG DESTN WAS YOUNGSTOWN, OH, BUT ITS WX WAS BLO MINS, SO THE FLT TO TRANSPORT A FOOTBALL TEAM WAS PLANNED TO ERIE WHICH WAS SLIGHTLY ABOVE MINS. THE COACH & BUSINESS MANAGER WERE NOT HAPPY ABOUT THIS, BUT PLANS WERE MADE TO BUS THE TEAM ON TO YOUNGSTOWN. EN ROUTE, THE MANAGER OCCUPIED A JUMPSEAT IN THE COCKPIT IN VIOLATION OF 14 CFR 121. THE WX AT ERIE DETERIORATED TO 100' OBSCD & 1/4 MI VIS WITH FOG. THE CREW ENTERED HOLDING WITHOUT CLNC TO WAIT FOR THE WX TO IMPROVE. THEY ELECTED TO MAKE AN ILS APCH (MINS 200' CIG & 1/2 MI VIS) & LEFT THE HOLDING PATTERN WITHOUT CLNC. AT APRX 2800', RADAR CONTACT WITH ATC WAS LOST, BUT THEY RECEIVED AN ABOVE MINS WX REPORT FM THE STATION AGENT & CONTD THE APCH WITHOUT AN ATC CLNC. THEY DID NOT ACTIVATE THE APCH LGTS. AT THE DH, THE COPLT SAID 'I DON'T HAVE IT', BUT THE CAPT SAW LGTS TO HIS LEFT & CONTD THE LANDING. THE ACFT LANDED ON SOFT GND BESIDE THE RWY & ROLLED TO A STOP WITH MINOR DMG. RWY LGTS AT STEP 1 INSTEAD OF 2 DUE TO A WIRING PRBLM. CAPT WAS ON DUTY APRX 15 HRS, AWAKE 19.5 HRS. 2 EMERG SLIDES MALF.