In my experience a technical co-founder's primary responsibilities are to be a visionary first, a hacker second and a manager third. first you recruit a tech co-founder to help visioneer what your product can, will and should do. then you have them support the one key part of the development process (prioritizing around the area of the technology with complexities or is part of your secret sauce) and then that person also manages whatever internal or external developers/technicians that are needed to launch or sale the product. Personally I think the evolution of the IT support model is better positioned as an "AND" play - meaning you find a competent technical partner that is cost accessible, scalable and reliable in terms of experience with similar startups and products. From there you continually look for a good fit CTO/tech co-founder and if you discover them early that is excellent, but do not force the issue (it is easier to scale down or replace a third party vendor, an equity holder not so much.)

Over the last 12 years my firm has helped 300+ entrepreneurs over thousands of projects plan, build, launch and scale their applications (all told raising about $700M in venture financing). So I've seen pretty much ever permutation of co-founder/CTO/product manager you can imagine in the startup space through the lens of my software development company. So if you'd like to connect and chat about how best to plan out the road ahead feel free to reach out.