There are a lot of great pcs that can be built for work in that budget. Are they going to be gaming at al? If they aren’t here is a build for around 500 that would be excellent
https://ca.pcpartpicker.com/list/hgNZQZ
That would be good and you could even add more ram or storage in the future. You can get a pretty good pc if you don’t need a graphics card and are fine with the igpu. If u wanted to spend a little more then here is another build
https://ca.pcpartpicker.com/list/F6jg3b
The basics is go with intel the onboard graphics on higher end chips is worth it and they are generally better. Get a cheap motherboard that is compatible. 8gb of ram is the minimum for 2018 16gb would be optimal. As for storage getting an ssd would be greatly beneficial for the speed, if u have extra money put it towards the ssd or a Mobo with more options.