My question is how do hosting and credentials work for sites built through Assembly? Who makes the $$$ outlay for a site? Does the project creator have to front and control things personally to begin with? Or is there some sort of arrangement where a particular company hosts in exchange an ownership stake and special status project members have rights to push changes through to 'live'?
In most cases, Assembly will help cover costs of things like domains and hosting during development, and in cases where someone in the community spent money on a product, that will be tracked and reimbursed when the product starts to earn revenue.
Also to clarify something in the comment below this one, Assembly's fee is 10% of the royalties paid back to contributors. (so, 10% of profit, not 10% of revenue)
