Actually even if you don't have these products/materials you can teach your child. You can have flashcards for words, bits of information, dots, etc. But you have to do it by yourself. Spend time for research, spend money for materials and a lot of work.
What do these products offer us? The program, the contents, and of course we save a lot of work and time. And that is what we are paying them for.
These products have different approach and have different contents. You can read so many opinions in the forum about these products and from there you can decide what you should have first.
But if you would ask me, with your situation, maybe it is best if you will buy YBCR first. As you know, YBCR has Volumes.
If you are really tight, you will not have to buy these Volumes all at once. You can buy the Starter Volume first. And your son can use this for a month. Next month, you can buy the 1st Volume and so on.
With LR and LM, you can have them for free through your points earned by posting to the forums, and uploading files.
Believe me, all of us wants to buy all these products. They are all good! But what stopping us?...MONEY!