What GPU would his mom need later on when the rig isn't for gaming? I'm sure he won't be putting a 1070 in here for Facebook and Youtube.
Sorry guys, I'm sticking to my guns on the prebuilt. There's a reason why similar spec'd machines are cheaper in this area and that's because you don't have to pay for the Windows license which saves 100 bucks right off the bat. For somebody who is only going to post cat memes by day and Farmville by night there's no point in worrying about whether it looks pretty, or really remotely perform any better than an internet box should. They will be stuffed into a corner and forgotten about until 7 years later when Youtube starts to lag then they will need a whole new machine anyways. My cousin is still using a Pentium D based machine with Vista to browse Facebook and do her grades on (she's a teacher). My immediate family miracast their phones to their TVs to avoid getting laptops or computers. If my mom asked for a computer tomorrow
this is what I'd get her and it'd still be better than the smart devices people use every day. Not only that but it's specc'd lower than the 350 dollar Dell I linked before. I get the want to build a fresh machine and the worry of upgrade later but the reality of it is it's not necessary for your average internet user.