Budget Build for Father-in-Law

So I actually posted this a while ago, wound up fixing his PC for the time being and we got him something else. The PC finally bit the dust a few days ago, so my wife and I are going to replace it for him as a Father's Day/Birthday gift.

My main concern up front is: is it even worth building something at this price point, or is there a pretty solid pre-built system I could get for him? I'm guessing pre-built is the way to go, any particularly good deals at the moment? If I could spend closer to $300 instead of $400 that'd be a plus too, but like I said I'll go to around $400 if it's a significant improvement.

Edit: Maybe something like this or this or this.

1) What will you be doing with this PC? Gaming? Photoshop? Web browsing? etc
It should all be very light usage. Email, web browsing, maybe some occasional work from the office on Access or Excel, accounting software, etc. The extent of gaming would be stuff like Candy Crush. I would've thought a laptop would be better, but he seems really set on having a desktop.
2) What's your budget? Are tax and shipping included?
I'd like to keep it at $400 or so max. I'd be willing to spend slightly more if it would be a significant upgrade (i.e. for an SSD or something)
3) Which country do you live in? If the U.S, please tell us the state and city if possible.
I'm in NJ. I'm close enough to the Paterson, NJ Micro Center that I could make that drive.
4) What exact parts do you need for that budget? CPU, RAM, case, etc. The word "Everything" is not a valid answer. Please list out all the parts you'll need.
Case, CPU, RAM, mobo, video card (if even necessary), hard drive, PSU, CD/DVD drive, and windows 10. He likes his current case, but it's ancient so I think it's gotta go.
5) If reusing any parts, what parts will you be reusing? Please be especially specific about the power supply. List make and model.
Peripherals only - keyboard, mouse, monitor, etc.
6) Will you be overclocking?
No.
7) What is the max resolution of your monitor? What size is it?
I believe it's a 19".
8) When do you plan on building/buying the PC?
Immediately.
9) What features do you need in a motherboard? RAID? Firewire? Crossfire or SLI support? USB 3.0? SATA 6Gb/s? eSATA? Onboard video (as a backup or main GPU)? UEFI? etc.
Like I said, this is going to be pretty light usage stuff. No specific requirements here.
10) Do you already have a legit and reusable/transferable OS key/license? If yes, what OS? Is it 32bit or 64bit?
No, we'll need a win10 license.

Should've jumped on the cyberpower item at newegg sooner I guess, price jumped up by $90.