All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
There is nothing wrong with giving financial support to your son who abandons the prayer so that his business improves and makes a profit, as long as you believe that this would most probably benefit him and would not result in wasting the money. You may utilize it as a means to call him to return to Allaah through offering the prayers. Remind him that he is in grave danger for abandoning the prayer, which is a pillar of Islam. Whoever abandons it has destroyed his religion and there is no share of Islam for the one who wastes it for his saying, sallallaahu ‘alayhi wa sallam: "Nothing stands between an individual and disbelief and polytheism except abandoning the prayer.” [Muslim]
Moreover, abandoning the prayer might be the cause of his misery and deprivation of provision. Thawbaan narrated that the Messenger of Allaah, sallallaahu ‘alayhi wa sallam, said: "Nothing increases one’s life time except dutifulness to one`s parents and nothing prevents the Decree except invocation. Indeed, the individual may be deprived of provision because of the sins he commits.” [Ahmad and Ibn Maajah; Al-Albaani: Hasan]
We advise you to invoke Allaah intensely to guide your son. May He Grant us and him and you and all Muslims guidance and success.