That only tells us the purpose of his relocation but the other questions remain unanswered.  We don't actually need the answers although you should consider those carefully as the responses would determine the tax residency of your client in IL, particularly if he plans to buy another house in IL and go back regularly.

In any case, what's the purpose of him buying another house in IL?  Will it be let out to a tenant at FMV?  Would it be left vacant for his use when he returns or during his visits?  If so, does he plan to claim homestead exemption?  These are some of the questions you should consider.

Unless your client can clearly establish, based on facts and circumstances, that the Philippines is now his domicile and there is no intention to return to IL in the foreseeable future and that his visits to IL would merely be temporary and transitory, your client would generally still be considered an IL resident.