Ok, former homeless person here. The following advice is based on my city, and may not apply everywhere.

You want to help a homeless person? Put away your wallet, don't even bother with food. In a big city its not a big challenge to have access to free food. If you want to give anything, give a clean dress shirt and slacks.

Be an advocate, and be a reference. Yeah, I lived with him for years, he's an awesome tennant. Yeah, I worked with him for years, he's a model employee. Help him navigate the system, because there are so many things the government offers you, but good fucking luck figuring all that out yourself, they certainly don't make it easy.