Help a homeless guy or leave him alone?

There’s an alcoholic homeless guy literally sleeping on my doorstep outside of my apartment. It does annoy me quite a bit because every time I go in I feel like he’s going to jump, stab me and get in the building or something. However, I also feel that I could help him – but then again, he is in a terrible situation, he can’t even speak alright.

So, the bottom line/question is – should the homeless be left alone or helped? Why?