I had a co-worker asked me about what computer to buy.
He has a 10 year old computer that he build but did not follow the new tech since then.
I asked him what he used the computer for and he told me email and surfing the net and not games or editing video and such (or watching movies).
I told him to buy a $300 to $400 (maybe $500) computer from like Cyber Power with 16 GB ram (probably overkill) and a SSD drive.
At least you get a guaranty of some kind and it would be cheaper than you build yourself.
Was I wrong with this advice?

Sounds like good advice but I normally give people a bit of headroom and would say more like a $500-600 system unless a tight budget is needed. Often times people with an old system do not realize the power of a new system and the entertainment options you now have with them. His old system could have been using WiFi and only the N bandwidth and take like a minute to load a Netflix video which might not have hit HD. Same problem could have happened with Youtube. I feel it's best to recommend something that you feel would be able to handle any entertainment options they want and that with a good video card added could handle almost any game.
 
That said a $400 system should still fit the needs pretty well and someone who spends $300 would know they probably are buying a budget computer.

I would have honestly just told him to go buy an iPad. If he doesn't do anything like games or even video an iPad would have been ideal. You can get last years 9.7in base model iPad for about $279 which has the exact same processor as this years 10.2in model or you could just opt for the current 10.2in model for $329 if he wants a slightly bigger screen. 
 
I'm saying this because if he doesn't do anything real intensive on his PC an iPad will let him surf the web, email etc....while he's sitting on the couch in the living room. And if he did want to game it just so happens that iPad has a metric $#it ton of games available for it and it's also great for watching Netflix or Amazon Prime. 

He does know about the new stuff does not want to play movies and such, but just wants to go cheap desktop, regular keyboard, mouse and a 27" screen.
Don't care about bells and whistles.

^not a bad build. I like it. But yeah for a basic build the original suggestion wasn't a bad idea at all.

& You'll be Tech Support for Life if you build it