I recorded a video for you guys, demonstrating that the machine type I recommended can easily handle video editing:
(click the cog, and speed this up to 1.5x)
EDIT: apparently I forgot to turn-on "record system sound" before I did the previous video, but you can see a sample, below.
In any case, yes, this machine can easily handle video editing, and yes, Ebay is generally the best place to get it in terms of safety and price-point.
Here is the video I made from my less than $300 machine with no dedicated graphics card:
(all in good fun)

The guitar sample, from the video demonstration, rendered just fine, btw...
View attachment 192097
SFF machines, btw, only have two RAM slots, so it's ideal to buy them with exactly the RAM you need.
Replacing it will actually waste your money, and cause extra trouble to install.
Plus, you'll have 4gb of SFF RAM, and nothing to do with it. (speaking from experience)
/end of try-hard thread reply