3658-3664 Marlborough Ave is a thoughtfully upgraded and fully permitted 4-unit property that strikes a rare balance between modern design, reliable income, and long-term flexibility. Set on a generous 7,003 sq ft lot with alley access, this multi-unit asset offers approximately 2,642 sq ft of living space and has benefited from extensive capital improvements designed to support low-maintenance ownership. The unit mix is both efficient and versatile. Unit 3658 is a studio of approximately 309 sq ft featuring high ceilings, an upgraded kitchen and bathroom, modern flooring, and newer foundation, roof, plumbing, and electrical completed within the last five years. Unit 3660 is the original residence and largest unit, offering 3 bedrooms and 2 bathrooms across approximately 1,258 sq ft on a raised foundation. Unit 3662 is a 2 bedroom, 1 bathroom unit of approximately 833 sq ft, located in the rear structure with both front and alley access and a newer roof. Unit 3664 is a fully permitted ADU of approximately 242 sq ft, thoughtfully designed with a new kitchen, roof, plumbing, and electrical. Shared laundry serves all four units, enhancing tenant convenience. Recent inspections reflect a well-maintained property, with recommended improvements largely limited to exterior systems, life-safety items, and preventative maintenance, reinforcing the overall integrity of the asset. This is a compelling opportunity to acquire a carefully executed four-unit property offering stability today with multiple paths for future optimization in one of San Diego's most dynamic urban neighborhood.