Per AC 20-139 Section 8....
"Commercial Assistance on Incomplete Aircraft. Commercial assistance does not include the instance where an incomplete aircraft is sold to another builder and the second or subsequent builder completes the aircraft. In such a case, the work performed by the first builder will count toward completion of the major portion by the second builder. The second or subsequent builder should obtain as much detailed information and documentation e.g., logbooks, material receipts, pictures, etc., from the original builder as possible. This information will be helpful in the FAA’s determination for the major portion requirement of the aircraft and eligibility of the subsequent builder to meet the requirement for repairman certification under section 65.104. The second builder may not be eligible for a repairman certificate under section 65.104, unless it can be shown to the satisfaction of the FAA that the individual has the requisite skill to determine whether the aircraft is in a condition for safe operation."
Justin