THE ACFT WAS BEING REPOSITIONED BY THE OWNER FROM A MAINTENANCE FACILITY AT BUFFALO INTL ARPT TO BUFFALO AIRPARK. MAINTENANCE PERSONNEL AT BOTH LOCATIONS WHO HAD DEALT WITH THE OWNER INDICATED HE HAD ATTEMPTED TO CUT COSTS BY PERFORMING UNAUTHORIZED REPAIRS HIMSELF. THESE REPAIRS WERE NOT COMPLETE PRIOR TO DEPARTING BUFFALO INTL. THE PLT OF N4708P ABORTED HIS FIRST TKOF STATING TO THE TWR '...I HAD A LITTLE MISS.' WITNESSES STATED THAT DURING THE SECOND TKOF THE ACFT CLIMBED TO ABT 50 FT THEN LOST ALT WITH THE NOSE PITCHING DOWN. THE RATE OF DESCENT WAS ARRESTED BEFORE GD CONTACT AND A SLOW 'MUSHY' CLIMB WAS INITIATED. THE ACFT NEVER EXCEEDED 300 FT ALT IN THE 5 MILE FLT TO BUFFALO AIRPARK. IT WAS OBSVD BY THE TWR SUPERVISOR TO OSCILLATE NOSE UP AND DOWN AFT EXTENDING THE LNDG GR FOLLOWED BY ROLLING TO THE RT AND SPINNING INTO THE GD APPROX 1 MILE E OF BUFFALO AIRPARK. INVESTIGATION REVEALED THE PLT HAD ACCUMULATED APPROX 50 HOURS TIME IN PA-23'S, 28 HOURS AS PIC AND 5 HOURS IN THE LAST 90 DAYS.