Anyway let's say you have a society where all the firms are worker self directed. It makes sense for firms to form broader organizations that represent different interests. So for example lets say you have an industrial zone on the edge of a geographic region. There's a shipping port, some bridges, electrical infrastructure, etc. All the firms in the area depend on this infrastructure to operate. And because they share this common interest, they have formed a regional cooperative made up of delegates from each firm in the region. When they need to make a decision about when to perform major infrastructure work, it is decided at one of their regular meetings. The delegates are not their to make their own decisions but to bring with them decisions made at their firm's meeting on the matter. If the delegate agrees to something their firm's people actually do not like, their people can recall them.

So the regional cooperative holds a regular meeting and there they decide they are going to build a bigger bridge and then decommission the old one. All the firms in this regional cooperative keep their money at a credit union which was set up specifically to represent these firms. They need to rustle up $500m to pay for this. They discuss how to raise the funds. There is a particularly big firm that will benefit substantially from the new bridge. They put up $50m on the condition that the bridge will have tolls and they will expect to be paid back $30m over 30 years. The rest of the firms together put in another $50m. The industrial zone regional cooperative takes their $100m to the broader regional cooperative which represents a large geographic region including several major cities which benefit from the industrial zone. The broader cooperative agrees to stake the other $400m for the bridge improvements with the agreement that the industrial zone regional cooperative will pay it back over 40 years.

So yeah. That's generally how you manage that. You can look up Murray Bookchin, David Harvey, and Richard Wolff if you want to know more. Also look up Zoe Baker on youtube.

If you don't like my made up scenario, maybe look up how ITER or LHC get their funding.

https://en.wikipedia.org/wiki/ITER#Funding

https://en.wikipedia.org/wiki/Large_Hadron_Collider#Cost

EDIT: Of course ITER and LHC are not workers cooperatives, just examples of how people delegating funds could make decisions.