Why are there enough stories to justify this group.

5848216 Because canon doesn't address obvious problems and we make various judgements based on what it doesn't tell us.

Actually, there are a lot more stories than you think where Sunset Shimmer is portrayed as homeless at least at some point through them. There are a lot of people that believe her to actually be homeless, because let's face it, they say nothing about her having foster parents or a job. And even if she staying in the school a lot like Twilight did, that is still homeless as sneaking in someplace to sleep and shower is still being homeless. I for one look forward to seeing what this group can gather/produce.

5848799 Could you kindly link me some of them?

5849483 Some of these may not be exactly what you are looking for as she isn't homeless throughout the entire story, but she is homeless at one point of another. This is only a few I can think of off the top of my head, but I will look for the others later and post more.
In a Time of Need by Small Muffin
H20 Just Add Friendship by Burning Sunset
A Second Chance to Find Home by Burning Sunset
Long Road to Friendship by the Albinocorn
7DSJ: The Three Sunrises by Shinzakura
My Best Friend: Sunset Shimmer by PinkieLunaShy
A Home for the Holidays by Twilight Nightmare
Goodnight Sunset, Good Morning Sunrise by Twilight Nightmare
A Knight in Shining Armor by Rinshi
From the Ashes by RC2101_Copey
Element Breakers by Demegor

This is just a quick search for stories I either have in my read later list or ones I could remember from memory and a quick search to find them. Not all of them is a street homeless Sunset as some of them she is living in an abandoned place like a warehouse or something. I'll try and do a more extensive search for more like the one called Alone or Abandoned or something similar where the girls follow Sunset to find her living in a tent and being attacked. I couldn't find it right now, butt I'll take more time later to search for more of the ones I have in mind.

5849777 Thank You gonna leave you with a little gift for your help.

5850788 Oh wow, thanks. Also, I'm still looking for others I remember seeing, especially the one. I just can't find it, and I'm beginning to think it may have been deleted because I want to think it was written by Small Muffin, but if it was then it's no longer there sadly.