Are the "ya" and "yo" needed in these sentences?

In a previous post, the following sentences were presented in the comments to demonstrate future tense:

Ya lo hago yo después. (I will do it later.)

Ya lo compraré cuando tenga dinero. (I will buy it when I have money.)

Te llamo más tarde. (I will call you later.)

Lo compro después. (I will buy it later.)

I'm wondering, do you need the "Ya" in these two sentences? Also, do you need the "yo" in the first sentence? Could you just say "Lo hago despues" and Lo compraré cuando tenga dinero"? Do these elements add anything extra?

submitted by /u/createdamadman
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