Add the Income and Asset classes.

lib/models/asset.dart

@@ -0,0 +1,19 @@
+import '/models/tracked_type.dart';
+
+class Asset extends TrackedType {
+  static String amountText = "Amount";
+
+  Asset({
+    super.id,
+    required super.name,
+    required super.amount,
+    required super.description,
+  });
+
+  factory Asset.fromMap(Map<String, dynamic> json) => Asset(
+        id: json['id'],
+        name: json['name'],
+        amount: json['amount'],
+        description: json['description'],
+      );
+}

lib/models/income.dart

@@ -0,0 +1,35 @@
+import '/models/recurring_tracked_type.dart';
+import '/models/frequency.dart';
+
+class Income extends RecurringTrackedType {
+  static String amountText = "Revenue";
+
+  Income({
+    super.id,
+    required super.name,
+    required super.amount,
+    required super.frequency,
+    required super.description,
+  });
+
+  factory Income.fromMap(Map<String, dynamic> json) => Income(
+        id: json['id'],
+        name: json['name'],
+        amount: json['revenue'],
+        frequency: Frequency.values
+            .where((freq) => freq.title == json['frequency'])
+            .first,
+        description: json['description'],
+      );
+
+  @override
+  Map<String, dynamic> toMap() {
+    return {
+      'id': id,
+      'name': name,
+      'revenue': amount,
+      'frequency': frequency.title,
+      'description': description,
+    };
+  }
+}