First we got a grant from the NLnet[1], which I highly recommend as a first step of any project. Single best thing I could have done. That wasn't enough money for me to quit my job. Also I didn't have any _evidence_ that IronCalc was a good idea or that there was a market for it. Then evidence started pouring and I kept working. I started talking to different folks, lots of people many of those were contacts through the NLnet. Then the folks from NextGraph[2] approached us and asked, "Hey do you want to be part of this consortium [3]?". Eventually we got a HORIZON grant after a lot of sweat and paperwork, but NextGraph took the brunt of it.
As you see there is a huge component of sheer luck
[1]: https://nlnet.nl/project/IronCalc/ [2]: https://nextgraph.org/ [3]: https://elfaconsortium.eu/