With today's computing power I'm not even sure an i5 is nessesary. For straight office/web work an i3 will have more than enough punch as long as its paired with a SSD and 8-16GB of ram.
I'd take the money saved from the i5, and put it into a larger SSD.
Don't forget though. When building your own computer it comes with zero "value added" software. Most of the time thats a benefit, no junk slowing it down. But that also means you need to purchase a copy of the OS you want to run, and any applications you might want, like MS Office.
An OEM copy of Windows 10 is about $110. MS Office is a bit more expensive. If there are any accounting apps like quicken, you'll need to buy those too. And I would also suggest purchasing a Anti-virus subscription. As well as either an online cloud backup solution, or one of the external hard drives that comes with Backup software built into it.
You absolutely do NOT want to get hit with a Locky virus. There is NO recovery from it. You cannot decrypt the files, its computationally impossible at this point. The only way to decrypt them is to pay the Ransom. Locky and other ransom ware uses a 2048bit RSA key, that randomly generates 128bit AES encryptions for each file. Each encrypted file uses a different AES key. The end result is total loss of any encrypted file.
An example. We got hit with it at work. Just a single user got the Locky virus. In just about 1.5hrs before it was reported and her computer removed from the network it had encrypted over 200,000 files. Over 200,000 business critical documents were permanently encrypted. Because we have a good backup solution, once we pulled her PC off the network, we just deleted all the encrypted files and did a restore from a known good backup to restore the missing files.
So for us, it was no biggie. But if we didn't have a backup solution? Those files would have been lost to us forever.