Using own squeezed lemon juice
Just because industrial food producers can create a safe process for a given preservation method, it does not mean that you can do it too. 

The best you can do in this case is to make canned juice, which, as long as it is in a closed jar or bottle, will last on the shelf for months and years. But as soon as you open it, you will only have 3-5 days in the fridge, after which you have to throw out that can. You also have to subject it to proper canning temperatures for a sufficiently long time, so it will not taste like fresh juice afterwards. Also, it is highly unlikely that you will see any savings - even if your own time costs nothing to you, fresh lemons are more expensive than bottled juice. 

Most people do not see the point in that and simply squeeze their lemons whenever they need juice. But if you want to go the canned route, you can simply follow any recipe for high-acid juice canning. And obviously, you don't need to acidify it extra the way it is done with other juices, since lemon juice is already more acidic than standard acidifiers like vinegar.