if i understand correctly you just need the PC and you already have screen keyboard and mouse? depending what programs you use for "work" you might be cheaper to buy a raspberry pi? if for engineering you use programs like CAD then no i dont think you can use a raspberry pi. there are programs like CAD like freeCAD.... though i have no experience with it so i cannot tell... since you are engineer and all...
https://www.raspberry-pi-geek.com/Archive/2016/17/3D-modeling-on-the-Raspberry-Pi-with-FreeCAD

I personally use a 7 year old broken laptop as a screen hooked up to a raspberry pi 4. Raspberrypi4 is the newest model of raspberry pi. starter kits with the newest model can cost 100€ but older ones are cheaper. you might even get cheaper by buying the parts separately or alternatives that are cheaper, but only do that if you know which parts u need.

I found the raspberrypi 4 starter kit with 4gb RAM and slightly faster quad processors costs 109€ but i think i saved a couple of euros just by knowing which parts to buy separately....

but starter kits of raspberry pi 3 (slightly slower quad processor and only 1GB of RAM) can be only 67€. (i use my raspberrypi 3 as a server)