In Jain dharma, his karma is primarily his own, because karma binds according to his intention, choice, and action.

If you donate with a pure heart to help someone in need, and later that person uses the money wrongly, then the bad karma of buying meat belongs to him, not to you.

However, in Jain ethics, we are advised to be careful and wise in giving:

• Give in a way that supports ahimsa.
• Avoid knowingly enabling हिंसा.
• If you know in advance that the money will be used for meat or other violence, then it is better not to give in that form.

So the simple answer is:

• No, you do not directly become the doer of his bad karma.
• Yes, if you knowingly support violence, your own karma can be affected by that intention.

Best Jain approach: help with compassion, but in a nonviolent and responsible way.