I once told an acquaintance friend of mine that I don't lend money, period. I'm happy to give them money (within reason) because money can come between good friends. Then I said that, due to my current situation (at that time, which she knew about) I was not in a position to be helping anyone else, financially. She's never asked me for a loan, since.

Having said that, she was known to use people, too.. for money, favours, etc. So I knew she was playing me at the time. So I empathetically declined.

In your situation, this does not sound like a balanced friendship. It sounds like he's using you and will likely always be asking for things, as long as you don't set that boundary.

At this point, I'd be honest. Tell him you've noticed a pattern of him needing you for financial support and it makes you uncomfortable. You don't have to explain further. You're not helping him by enabling.