What's the earliest stage a startup should consider hiring a customer success manager?

Whenever there are customers you need to retain (psst... that's pretty early!).

I've found that we in the industry are quite liberal in what we call Customer Success, particularly in early-stage companies. You'd likely start with a CSM as the person who helps onboard/implement the new customers, answers how-to questions for them, and does whatever it takes to make their product dreams come true. The role is broad and a catchall for post-sale needs. Who would do it otherwise? You probably don't want your sales rep taking time away from growing the company, nor do you want every customer question and complaint hitting the founders.

Over time, you'll mature and specialize the CS function as you introduce other specialists in Implementation, Technical Support, etc. and beef up customer resources like in your knowledge base and community.

For that first hire, consider someone who is a product expert, customer-obsessed, and a pro at getting things done cross-functionally. A high-potential hire could go on to lead a team of CSMs as you grow.