IMHO, the thing to consider is that anyone worth bringing in as the technical lead for a startup that's in as early a phase as your seems to be would ALSO be so

IMHO, the thing to consider is that anyone worth bringing in as the technical lead for a startup that's in as early a phase as your seems to be would ALSO be someone who's quite capable of starting their own startup. You need to be able to explain to your candidate why they should bust their butt without pay on your startup, instead of working on their own startup. As many others on this thread have pointed out, offering a full founder/CTO position should do it.