Is it permissible to divorce the second wife due to infertility, so that the husband can marry a third wife in hopes of having children, in the event that he cannot keep both of them? And is it possible to move the first wife to a more luxurious house, leaving the second wife in an older house?

Divorce is permissible out of necessity, including the desire to have children. However, it is better not to rush into divorce and to seek medical treatment. As for preferring one wife over another in housing, it is permissible as long as each wife has sufficient provision. He may also prefer one over the other in terms of expenses, clothing, and desires, provided that the other wife also has sufficient provision.