How Should I Invoice a Client for Azure Services?

You have a couple of options:
1. Ask your client to create a tenant/subscription and give you the rights to build the backend.
2. Alternatively, if you create a subscription under your account, you can pay it yourself and then invoice your client, maybe with a small markup for your time. Just make sure to keep an eye on the costs and avoid any expensive resource checkboxes!

It sounds like you might want to get a tenant set up for your client. This way, you can charge them what Azure is charging you without any hassles. At the end of the project, you can just transfer everything over to them. Keep it simple and straightforward!

If there's already a tenant, use that for your work and invoice them. If not, creating a new one might be worth it, but just be careful about putting your credit card on it. You wouldn't want to risk any unexpected overcharges. Ideally, you should create a tenant for the client and then bill them for the services you provide.

You can definitely set up the subscription under your tenant and manage the billing. That way, you can invoice based on their usage or perhaps a fixed fee. Azure's Cost Management + Billing feature will help you keep track of expenses.

Consider becoming a CSP partner with Microsoft. This allows you to earn a kickback of 10%-30% on your client’s subscription bill. You would need to manage the invoicing yourself, which is pretty straightforward. Plus, you can add clients and subscriptions through the CSP partner portal, allowing you to mark up your profits!