Here's one. It's not the latest tech but it makes ideal office PC:
PCPartPicker part list /
Price breakdown by merchant
CPU: Intel - Pentium G4560 3.5GHz Dual-Core Processor ($67.79 @ OutletPC)
Motherboard: MSI - B250M PRO-VDH Micro ATX LGA1151 Motherboard ($59.99 @ Amazon)
Memory: G.Skill - NT Series 8GB (2 x 4GB) DDR4-2400 Memory ($65.99 @ Newegg)
Storage: Crucial - MX500 250GB 2.5" Solid State Drive ($54.95 @ Adorama)
Storage: Western Digital - Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($45.89 @ OutletPC)
Case: Thermaltake - Versa H15 MicroATX Mid Tower Case ($34.44 @ Amazon)
Power Supply: SeaSonic - EVO Edition 620W 80+ Bronze Certified Fully-Modular ATX Power Supply ($55.06 @ B&H)
Optical Drive: Asus - DRW-24B1ST/BLK/B/AS DVD/CD Writer ($21.65 @ OutletPC)
Wireless Network Adapter: Gigabyte - GC-WB867D-I REV 4.2 PCI-Express x1 802.11a/b/g/n/ac Wi-Fi Adapter ($39.99 @ SuperBiiz)
Total: $445.75
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2018-10-18 23:23 EDT-0400
Few words
Build itself is micro-ATX due to the smaller MoBo and case used, which is good since in the office, there isn't usually much space where to put mid-tower ATX PC. Since CPU has on-board graphics, dedicated GPU isn't needed, saving a lot of money. MoBo has 4x RAM slots, making any future RAM upgrade very easy (not that it's needed for this build anyway). For storage, SSD is best price to performance ratio and well enough in capacity for OS and additional software. You can remove HDD if you want to save some money but extra space could come handy. Case is standard office PC looking one, meaning no side window. If your folks doesn't use CDs, DVDs, you can also remove the ODD to save money. Also, if PC is connected to the net via cable, you can remove the wi-fi adapter as well. And lastly, PC is powered by good quality and fully-modular PSU.
If needed, that PC can be upgraded to high-end, 4K gaming rig with 3x simple upgrades:
CPU: from G4560 to i7-7700
RAM: from 2x 4GB to 4x 4GB (with 2nd 2x 4GB 2400 Mhz set)
GPU: from none to GTX 1080 Ti (since 620W PSU can handle GTX 1080 Ti with ease)
Here's the same build as above but with all the extras (HDD, ODD, wi-fi card) removed,
pcpp:
https://pcpartpicker.com/list/hXQ2TB
Note: to save even more money, you should be able to use your 2x Kingston DDR4 RAM DIMMs, making the purchase of G.Skill RAM unnecessary. With all the extras stripped and when using your Kingston RAM, you can make the whole build sub $300.