From what you've said, it's clearly not the type of business that's going to produce an immediate income such as can be gained from buying wholesale and selling items at a profit etc, OP.
How long do you estimate you have before your funds run out and the wolf will be at the door? Are you in the UK or in a country that provides the safety net of welfare benefits?
As my experience is that what the CEO says goes, I find it surprising that your dh wasn't given carte blanche to expand the company, so to speak, by being given the specified role of developing this new but related venture and, sadly, this leads me to conclude that it wasn't considered a financially viable proposition for him to do so - in short, imo your dh has been snowing you.
That's not to say that he won't be successful in going it alone, but the field of events/conference management is extremely competitive with many organisations preferring to utilise the services of those long-established agencies they have built a solid relationship with over many years.
For businesses such as appears to be what your dh is endeavouring to set up, there can be a long wait before services rendered become services paid for and it's unclear why your dps have been tapped unless venues have been booked and it's now a question of getting bums on seats to recoup the sums invested in accomodation/publicity.
FWIW, resigning with 'immediate effect' usually means that your dh will be paid up until his day of employment which would seem to be today.
I wish you both luck and also wish I could be more optimistic about your future prospects if he continues to put pie in the sky before pie on the table.