diff --git a/app/Enums/BusinessStatus.php b/app/Enums/BusinessStatus.php
new file mode 100644
index 0000000..d057b53
--- /dev/null
+++ b/app/Enums/BusinessStatus.php
@@ -0,0 +1,57 @@
+<?php
+namespace App\Enums;
+
+/**
+ * 견적 상태 코드 Enum
+ */
+enum EstimateStatus: string
+{
+    case Draft      = 'draft';      // 임시저장
+    case Submitted  = 'submitted';  // 제출/확정
+    case Approved   = 'approved';   // 승인
+    case Rejected   = 'rejected';   // 반려
+    case Cancelled  = 'cancelled';  // 취소
+
+    // 한글라벨 등 커스텀 메서드
+    public function label(): string
+    {
+        return match($this) {
+            self::Draft    => '임시저장',
+            self::Submitted => '제출/확정',
+            self::Approved => '승인',
+            self::Rejected => '반려',
+            self::Cancelled => '취소',
+        };
+    }
+}
+
+/**
+ * 주문 상태 코드 Enum
+ */
+enum OrderStatus: string
+{
+    case Created    = 'created';
+    case Confirmed  = 'confirmed';
+    case InProgress = 'in_progress';
+    case Completed  = 'completed';
+    case Cancelled  = 'cancelled';
+
+    // 한글라벨 등 커스텀 메서드
+    public function label(): string
+    {
+        return match($this) {
+            self::Created    => '등록',
+            self::Confirmed => '승인',
+            self::InProgress => '진행중',
+            self::Completed => '완료',
+            self::Cancelled => '취소',
+        };
+    }
+}
+
+// 사용
+/*foreach (EstimateStatus::cases() as $status) {
+    echo $status->name;
+    echo $status->value;
+    echo $status->label();
+}*/
diff --git a/app/Models/MainRequest.php b/app/Models/MainRequest.php
new file mode 100644
index 0000000..bb83d92
--- /dev/null
+++ b/app/Models/MainRequest.php
@@ -0,0 +1,50 @@
+<?php
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\SoftDeletes;
+
+class MainRequest extends Model
+{
+    use SoftDeletes;
+
+    /**
+     * 통합 업무 마스터(견적/수주/발주/작업 등)
+     */
+    protected $table = 'main_requests';
+
+    protected $fillable = [
+        'tenant_id',
+        'status_code',
+        'description',
+        'created_by',
+        'updated_by',
+        'created_at',
+        'updated_at',
+        'deleted_at',
+    ];
+
+    /**
+     * 전체 이력(흐름) 리스트
+     */
+    public function flows()
+    {
+        return $this->hasMany(MainRequestFlow::class, 'main_request_id');
+    }
+
+    /**
+     * 견적/수주/발주 등 파생 업무별 관계 (예시)
+     */
+    public function estimates()
+    {
+        //return $this->hasMany(MainRequestEstimate::class, 'main_request_id');
+    }
+
+    public function orders()
+    {
+        //return $this->hasMany(MainRequestOrder::class, 'main_request_id');
+    }
+
+    // ... 필요에 따라 파생 업무별 hasMany 관계 추가
+}
diff --git a/app/Models/MainRequestFlow.php b/app/Models/MainRequestFlow.php
new file mode 100644
index 0000000..23acb43
--- /dev/null
+++ b/app/Models/MainRequestFlow.php
@@ -0,0 +1,41 @@
+<?php
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Model;
+
+class MainRequestFlow extends Model
+{
+    /**
+     * 업무 전체/상세 흐름 이력(폴리모픽)
+     */
+    protected $table = 'main_request_flows';
+
+    protected $fillable = [
+        'main_request_id',
+        'flowable_type',   // 폴리모픽 타입(모델명)
+        'flowable_id',     // 폴리모픽 PK
+        'status_code',
+        'action',
+        'content',
+        'actor_id',
+        'created_at',
+        'updated_at',
+    ];
+
+    /**
+     * 메인 업무 엔터티
+     */
+    public function mainRequest()
+    {
+        return $this->belongsTo(MainRequest::class, 'main_request_id');
+    }
+
+    /**
+     * 폴리모픽 관계(견적, 주문, 발주 등)
+     */
+    public function flowable()
+    {
+        return $this->morphTo();
+    }
+}
diff --git a/app/Repositories/MainRequestRepository.php b/app/Repositories/MainRequestRepository.php
new file mode 100644
index 0000000..63328fb
--- /dev/null
+++ b/app/Repositories/MainRequestRepository.php
@@ -0,0 +1,44 @@
+<?php
+namespace App\Repositories;
+
+use App\Models\MainRequest;
+use App\Models\MainRequestEstimate;
+use App\Models\MainRequestOrder;
+use App\Models\MainRequestFlow;
+
+class MainRequestRepository
+{
+    // 메인 업무 단건 조회
+    public function find($id)
+    {
+        return MainRequest::with(['flows', 'estimates', 'orders'])->find($id);
+    }
+
+    // 견적 생성
+    public function createEstimate($mainRequestId, array $data)
+    {
+        $data['main_request_id'] = $mainRequestId;
+        return MainRequestEstimate::create($data);
+    }
+
+    // 주문 생성
+    public function createOrder($mainRequestId, array $data)
+    {
+        $data['main_request_id'] = $mainRequestId;
+        return MainRequestOrder::create($data);
+    }
+
+    // 이력(Flow) 기록
+    public function addFlow($mainRequestId, $flowableType, $flowableId, $status, $action, $actorId, $content = null)
+    {
+        return MainRequestFlow::create([
+            'main_request_id' => $mainRequestId,
+            'flowable_type'   => $flowableType,
+            'flowable_id'     => $flowableId,
+            'status_code'     => $status,
+            'action'          => $action,
+            'actor_id'        => $actorId,
+            'content'         => $content,
+        ]);
+    }
+}
diff --git a/app/Services/EstimateService.php b/app/Services/EstimateService.php
new file mode 100644
index 0000000..941a6ad
--- /dev/null
+++ b/app/Services/EstimateService.php
@@ -0,0 +1,59 @@
+<?php
+namespace App\Services;
+
+use App\Enums\EstimateStatus;
+use App\Repositories\MainRequestRepository;
+use App\Models\MainRequestEstimate;
+
+class EstimateService
+{
+    protected $mainRequestRepo;
+
+    public function __construct(MainRequestRepository $mainRequestRepo)
+    {
+        $this->mainRequestRepo = $mainRequestRepo;
+    }
+
+    /**
+     * 견적 신규 등록
+     */
+    public function createEstimate($mainRequestId, array $data, $actorId): MainRequestEstimate
+    {
+        $estimate = $this->mainRequestRepo->createEstimate($mainRequestId, $data);
+
+        // 상태 이력 기록 (draft)
+        $this->mainRequestRepo->addFlow(
+            $mainRequestId,
+            get_class($estimate),
+            $estimate->id,
+            EstimateStatus::Draft->value,
+            '등록',
+            $actorId,
+            '견적서 임시 등록'
+        );
+
+        return $estimate;
+    }
+
+    /**
+     * 견적 상태 변경
+     */
+    public function changeEstimateStatus(MainRequestEstimate $estimate, EstimateStatus $newStatus, $actorId, $memo = null)
+    {
+        $estimate->status_code = $newStatus;
+        $estimate->save();
+
+        // 이력 기록
+        $this->mainRequestRepo->addFlow(
+            $estimate->main_request_id,
+            get_class($estimate),
+            $estimate->id,
+            $newStatus->value,
+            '상태변경',
+            $actorId,
+            $memo
+        );
+    }
+
+    // ... 기타 견적 비즈니스 로직도 여기에!
+}