- how much money you are ready to spend on the new guy.
- how long he and you expect to work together. I.e you want some one for next couple of years to build and setup everything, do you expect him grow and mature with you .
- CTO is a glorified role in a start up especially early on. At this point you are more likely to need a hands on senior dev who has strong product sense and can run a team and ready to gets hands dirty on code.
There are few people who will fit at all stages. Either they should be able to grow or be able to step down few roles today.
So plan accordingly for the new hires to replace when skills don't fit with what equity you would give today and later on etc.
On skills you should consider today somebody who knows the stack , is ready to code, has architecture vision , can be quick and dirty if required but prefers to keep the code clean as possible and is flexible on the resources you are able to give, loves building products.