I wouldn't suggest white-labeling, at least not in the crypto exchange field. Even though there will be no struggle as these products are usually easy to deploy, you will find a hard time with both support and most importantly, the customization of your exchange, not to mention that in most cases, you have to pay in an annual/monthly basis.

Open source products are out of the question as well (If you don't have the necessary knowledge), you don't know If these are secure enough and whether they contain backdoors or not.

Building your own exchange and hiring the right team might be time consuming and hard, but If done right, it would be very profitable. But again, If one is serious about running a business, no shortcuts should be used.