You should not accept this contract.

You are being asked to accept liability for people without an incentive to deliver good work of whose reputation you don't know.

The more unspecified the liability and acceptance/delivery or services description is, the more likely you are to end up with an endlessly "unhappy" client who won't make more payments but won't say it's all finished.

I suggest you run. Never take liability without responsibility, especially not without any large upside possibility. In the absence of clarity, clients will try and argue that you own the liability because you directed other people for the final product. You want to specify details and work against them with a healthy 20% buffer of extra quality/work to make sure the client can never argue you didn't fufil the work. This is the opposite of that. Don't do it.