Hi Nelson,
I’m new to the group here but I’ll give you my 2 cents.
You may know all this already but I’ll post what I know.
You should be editing to a seperate HD then your system drive(sure you are)
.avi files are very large and can be much bigger than your original files.
you do not need to render to .avi.. only then to render again to mpeg 2
just render your project to mpeg 2 from your timeline
you can also render it to mp4 for youtube
I have a 1TB drive with many projects on it but drive space is cheap today so 2TB might be the way to go if it’s in your budget.
hope this helps