From Border to Base
San Diego’s Best Residential
Property Management Company
Maximize profitability, minimize hassle. CoSine Real Estate makes rental property ownership simple, efficient, and transparent. For a flat 6 percent fee, owners gain full-service management, from marketing and leasing to maintenance and accounting.
Our advanced technology platforms streamline rent collection, maintenance requests, reporting, and tenant communication, giving owners real-time insight and total control. With hundreds of properties across San Diego, we combine local expertise with proven systems to protect your investment, reduce vacancy, and optimize returns—all while making ownership effortless.
Our Story
12 Years of Service. Hundreds of Owners. Thousands of Tenants.
CoSine Real Estate is a San Diego based management firm built on reliability, transparency, and long term performance. With more than three hundred homes under management and two decades of experience, we support investors, owners, and residents with professionalism and technical expertise. Our platform combines local knowledge, refined systems, and trusted vendor relationships to protect and enhance each property. From single family homes to multifamily portfolios, our focus is always the same: protect, maintain, optimize.
San Diego
CoSine Team
Management Portfolio
Since Our Founding
Our Services
Everything an investment property owner needs.
Exceptional management combines people, process, and technology. CoSine delivers all three in one seamless platform. Clients receive full service management that includes marketing, leasing, tenant placement, maintenance coordination, accounting, reporting, and brokerage support. Our 6 percent flat fee covers everything. No add-ons. No hidden charges. Just consistent, professional management designed to protect your investment and deliver clarity and confidence every step of the way.
6% Flat Fee
A single, all-inclusive rate covers every aspect of management. No hidden charges, no contracts, no surprises. You get full access to our technology, vendors, and professional services, all designed to protect and grow your investment.
Advanced Automation
Our integrated platforms streamline every process — from tenant applications and payments to accounting and reporting — giving owners real-time visibility and tenants a seamless, responsive experience.
Extensive Marketing
We fill vacancies quickly using aggressive, multi-channel marketing across every major rental platform. Automated showing software, follow-up communication, and our network of past tenants ensure consistent exposure and faster occupancy.
Professional Leasing
Only qualified, pre-screened tenants are placed in your property. Thorough background checks, legal-compliant leases, and digital documentation protect your property and minimize risk.
Total Maintenance
We manage repairs from start to finish, coordinating trusted vendors, tracking costs, and providing detailed reports. Regular inspections and proactive oversight preserve property value and tenant satisfaction.
Accounting & Reporting
Full transparency, real-time access, and comprehensive reporting give owners complete control over income, expenses, and financial performance. Monthly draws are direct deposited for convenience.
Buying & Selling
In addition to management, CoSine assists owners in expanding or liquidating portfolios. Our expertise in market positioning, due diligence, and negotiations ensures informed decisions and optimized financial outcomes.
We Make It Easy
Our 100% Satisfaction Guarantee
We believe good management earns trust. CoSine charges only on rent collected, offers no-term contracts, and never adds extra fees. If a property is vacant, you pay nothing. If you are ever unsatisfied with our service, you can walk away. No penalties, no fine print. We stand behind our work because we know it holds up.