A question for free market advocates?

I know most free market advocates are libertarians and i understand that they firmly believe in voluntaryism and not state coercion. But what if a segment of private sector voluntarily establishes a contract with the state? Ie acquiring government funds and operating the business according to the government rules that were stipulated in the contract? Free market is a strict separatist philosophy of state and the market, do libertarians believe in coercing the business-state collusion into seperation?