I ran my first startup as a "We don't pay ourselves" kind of thing. Actually mostly me, the other founder was side-jobbing as a freelancer.
I'm not sure how big a factor it was, but being dirt poor did not help that startup. And it just hurt all that much more when it all came tumbling down.
I think your problem is not because you don't have a side job. It's all about how to deal with partnership type of business.
If you don't have external funding, cofounders may choose to bootstrap the company, but you must have written down contracts about how the partnership will go, and register it with city/county or the State of Secretory. If you don't, you may hurt all of you no matter you all have income or even if you are rich. And the partnership cannot last long without such kind of contract and agreement. Some startups failed even before the fund pending because the partners cannot agree on the equity distribution.
I'm not sure how big a factor it was, but being dirt poor did not help that startup. And it just hurt all that much more when it all came tumbling down.