You start by doing it yourself. This is super important. Doing support brings you closer to your customers to understand their pain points so you can build a better product.

Technical question that they don't get? Either make it more explicit in your product, on your sales page or in your documentation. Once that's solved you should better understand customer needs and have fewer support tickets coming in.

Billing can be a little more painful but with a solid FAQ and some email templates over time this should resolve itself pretty quickly.

Non-product related enquiries (usually like billing) are the first ones you might outsource to someone else to handle. You can use services like influx.com to handle this.