Both of those are really too small for 8 chickens. In your area, a tight housing space is more doable, but those run spaces are tiny too. You really need around 80 sq. ft of outdoor space as a minimum unless they free range (in your yard in your case) most of the day, every day...at least if you want to avoid behavioral problems. The youtube guy was being generous in saying his housing might work for 6 hens...in that set-up, I couldn't even see how you'd manage an extra roost without the nest boxes getting pooped into overnight. In largest of the other tractors- that would only give 4 sq. ft of outdoor space per bird...less than half of what's recommended. It'll seem really spacious when your chicks are small -but will seem really crowded when they're the size of housecats.
Why don't you do a search on hoop coops or hoop runs. You can get a lot of run space without too much money with that model. I don't think you guys get much snow or cold do you?? So do a decent sized run and build your own simple housing if you have basic carpentry skills. Maybe attach two dog houses together (you can often get them cheap or free on CL) and modify??? You can put something together (coop/run) for $400 if you have some carpentry skills. If you're carpentry-challenged, then it'll be a bit more difficult to stay under budget, especially if you have time constraints.
Good luck! I know it's tough when you're first getting started with chickens, getting set up and all.
I agree with those coops being too, too small. Imagine you are a chicken....how would you want to live? Roomy quarters or really cramped quarters? Keep in mind that any given time your roommates may want to chase you and peck your head really hard! Do you want a some room to run or do you want to be trapped in a small area of corners?
I also agree with the ease of building a hoop house that is lightweight and movable but I would not use PVC material. I'd stick with cattle panels overlaid with welded wire and tarping. Easy to build in a few hours by anyone...anyone can put together a hoop house, even one person. You don't have to be handy at all....just be able to use a hammer, nails, zip ties, staples, etc.