This won't be the last deal you ever get offered.

There is nothing to suggest that the same opportunity won't be here in a year...particularly with a developer at risk approach. And the fact that they're not throwing a little cash at it upfront means maybe it's not a critical issue (or they don't have the cash).

Based on the idea that you don't have cash in hand, it's hard to see how it meets your immediate needs or allows you to develop your current enterprise.

Just structuring and enforcing a no money down deal itself is going to take time, energy and lawyers. Could those resources be better invested in your startup?

There's nothing wrong with passing on a deal due to timing.