Home services is where it's at. hVAC, plumbing, roofing, landscaping, pest control - most have awful websites, zero SEO, and the owner is the one picking up the phone. They get ROI immediately: you bring leads, they pay. No micromanaging. a few extra jobs a month and your retainer covers itself.
Another hidden gem is local med spas and aesthetics clinics. High-margin services, hyper-local audience, and they're still running on word of mouth. first agency to build a real digital presence for them owns that relationship for years.
i'd skip restaurants (thin margins, high churn), real estate (every agency is already there), and e-commerce unless you want to fight five hundred others for the same clients.
Pick one niche, build three solid case studies, and your cold outreach response rate will triple. Generic positioning is the death of cold email - be specific, be helpful, and own your space.