As you’ve discovered, there often is a fine line between helping someone and actually harming them–and sometimes it’s very difficult to know exactly where that line is.
In other words, when someone is facing a real need we should do everything we can to help them–not just meeting their physical needs, but helping them get on their feet. The Bible says, “If anyone has material possessions and sees his brother in need but has no pity on him, how can the love of God be in him?” (1 John 3:17). But if they are only taking advantage of us, we are actually hurting them if we fail to make them act responsibly.
Is this your son’s situation? Only you can tell–but you and your husband need to be in agreement on this, and share your concerns calmly but frankly with your son. Tell him that you love him, and because you love him, you want what is best for him. You might find it helpful to set a deadline for him to find a job and move into his own apartment (and even offer to help him with the rent for a month or two, if you can).
The most important thing you can do, however, is to encourage your son to open his heart to Christ and seek God’s will for his life. God loves him and knows all about his situation, and He knows too what is best for him. Jesus’ promise is true: “Seek and you will find” (Matthew 7:7).