Well, I read through what you have available and I've some critique for you.
First thing's first: Your novel is in First Person so, some of the troubles you're having is getting in description while remaining within the character's narrative. This IS a hard thing to do, first person POV isn't easy. From the outset of your first post, one of the problems you have is that you tend to ramble on details that are unimportant to your story and don't actually seem to be part of a quirk of Greg's mind. Not only that, but they're told in a very play-by-play fashion. To paraphrase things we start with: "I live in a big city, I'm homeless, it sucks, I'm hungry." And in reading what you have, it feels very much like I'm being told a story second hand by someone who heard it from someone else. What this means is you're struggling with Passive Voice.
Now, Passive Voice has its place, however if your entire novel is written that way you're going to have a hard time getting an audience engaged. That's because, we're taken out of the action. The entire scene where Jake saves Greg and the Cop turns on Greg feels very slow and I have no actual care for the main character's survival, because I can't "feel" his fear. You've run into the telling, rather than showing issue where we're told something is happening, but there aren't the right descriptors in place to really punch it up and make the audience feel like they're IN the story. I'll make some examples of changing things up so you can see the difference, starting with your first paragraph:
Original: I wake up on the hard, cold, concrete. My first thought is how lucky I am to get a full nights sleep for once. My body sore, I get up on two feet, grab my trusty hat and start begging for money.
I'm in the city. Lights flash everywhere, giant buildings surround me, and cars zoom on the street like there is no tomorrow, Paying zero attention to me. the poor, old, beggar with messy black hair and dead blue eyes. I would love to enable my fury at them. But, something inside tells me, that I would do the same as they do to me if the roles were reversed, ignore the broke man.
Edited: Another rough night on cold hard concrete and aching bones reminded me what a lucky bastard I am; I stretch the cold outta my muscles and snap, crackle, and pop my way to my feet. Yeah, I'm one of those 'hat in hand' suckers but hey, money is money.
The city is wakin' up to rosy sunshine on office windows, the smell fresh brewed coffee mixed with exhaust, shiny new doughnuts and of course, payin' zero attention to me. One look into my dead ol' eyes will cure anyone of wanting to spare a dime and still, I've got my hat in my hand. My hair looks like the matted rear of a Puli, and I can't tell if it's still black or if the mud has taken over. I probably smell about as charming as a leaky sewer pipe and yet here I am, hat in hand. People look at the ground when they walk by me, but for a second, I see their eyes dart in my direction. I know they see me, but they want nothin' to do with me. I wouldn't either.
See the difference in how the scene is built? You're missing a lot of sensory information that tells us, the audience, what the city FEELS like. You don't have to go into extreme detail, but you want to build the scene in their minds. There's also the problem of Greg listing out a bunch of descriptors, without really having a voice of his own. This creates a problem in the first paragraph, when he's listing off all the reasons people don't help him. It makes him come across as if he's saying the authors thoughts, rather than having his own. The reason IS because he doesn't have a 'flavor' yet. Everyone has thoughts in their head narrated in a certain voice and if you narrate, say in a rough tone (which is what I imagined when thinking of Greg's predicament) his thought patterns should reflect this, so we as the audience can get a sense of his personality.
I read through all of your posts and I still don't really FEEL like Greg has his own voice that is distinct, it just sounds like he's listing off events without really being part of them, even though he very much is. One thing I'd recommend since you are writing this in first person, is to read some first person novels (whatever favorites you have) and see how the main character's talk in their narrative. This will give you a good barometer to work with. Now, moving on from that, there are some technical things: there are words that aren't capitalized when they should be, commas that need to be periods and overall very simple sentence structure. Now, there's nothing wrong with a simple sentence, but when you write something with short sentences it feels very start and stop. Case in point this part here:
Original: Why did I ever let myself descend this low, I think to myself? Just the thought of asking for quarters irritates me. So, I vent out some of my anger by throwing my hat at a building. A couple of dimes and a penny clinked on the ground. That was all the money I had made last night. So, this is what it's like being homeless. I thought people were generous! I know some people are greedy, but, a hundred cars have already passed me in two minutes. three of them being racecars! Yet, no money has been given.
Edited: How could I let this happen? I crumpled my hat in my shaking fist and hurled it at the pavement, my paltry two dimes clinking out of it. Twenty damn cents. My face burned hot as I struggled to swallow a howl of frustration. Cars zizzed by leaving exhaust and no never mind; people walked on and paid me in sidelong glances and a heap of shame. So much for the generous human spirit.
You'll notice I cut a LOT of details out of this. First off, you don't have to have speech tags such as "I think to myself" because they're unnecessary. We know the character is thinking to himself because we're watching from HIS perspective so, instead, when he has a thought you should put the thought in italics. This will punch up the pace of your narrative which gets slowed down with the unnecessary tags and can often turn off readers. Now, aside from that, we still have the problem of too many passive descriptions that don't give us any emotion or flavor, we're TOLD he's angry, we're TOLD about the cars, we don't feel them go by, we don't HEAR or FEEL his troubles, we're just being told they're there. So, I went in and sprinkled in details like his face turning hot, his fist shaking, and stink of exhaust or the way people looked at him. This builds atmosphere and allows the audience to feel how Greg feels.
I've also used more complex sentences because, another problem you have is the start-and-stop that comes about with sentences being too short and then instead of using semi-colons, you just use a period it comes out almost like a robot. Here's an exercise you can do to see if you're running into this problem. Read your story out loud and whenever you come to a period, stop for five seconds. If you find yourself stopping too much, rework the sentence. People have a more natural flow when they speak and since you're writing in first person, you're going to have to find that flow so Greg doesn't sound by the numbers robotic. Giving him a more natural human sound (like narrating in his own voice, giving him his own mannerisms beyond his opinions) will be a good intrigue for an audience.
You've already been filled in on other technical stuff with regards to punctuation so, I won't go into that too hard, you'll be able to catch it while you're editing. The next thing I actually wanted to mention was, essentially, your dust jacket. This is the blurb on the side of the page that gives someone an idea as to what your story is about. Rule of thumb is, if the description is too long you'll lose interest. One of the things you have to do for a dust jacket, is get the general idea across without revealing too much of the plot. The best way to do this is to think of these three things: What is Greg's Goal, what will Greg have to sacrifice, and what are Greg's road blocks. Write one sentence for each thing and work it into a single paragraph that describes your story, without giving too much away. This can operate as a hook and really catch eyes if done well. Just remember the rule: Keep it Simple.
So that's the advice I have for you. This is just a first draft so one thing I'll say is this: Don't be discouraged, the things that I've mentioned here are the things every novelist has struggled with since the beginning of time! Fact is, you actually have the bones of a good story here and I think you could REALLY make your first person POV work for this guy because he's in a unique position being homeless and having to figure out supernatural elements. Just mind your technical stuff, use more complex sentences and try to include more sensory information so the audience can feel how Greg feels. Don't worry, your novel will get there in its own time with some editing and I'm sure you've got the chops to do it.