You could buy them outright, or you could persuade them into working for you if you can prove that you'd offer more security than their thievery gives them. High risk and high reward is all well and good, but consistency might be more worth it in the end, particularly if they have family to take care of.

[it does come with the risk that they might steal from Ryouma, but hopefully the deal meant it would work in their favor for them not to.]

But I don't know very much about how all this is supposed to work, so it could be a perfectly silly idea. You're welcome to correct me.