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)
Oh thank you for the information, the truth is that I am not very familiar with what computer terms are, being sincere I always turn to my brother and he tells me what I need, for the moment I had stopped working with programs like AutoCAD but I do need to work with budgeting programs and civil works projects, which demand a little more from me.
Today they tell me what I will need, but they already told me that the prices are approximately similar to what you tell me here, and as you say in effect I only need motherboard and processor, I'm not sure if the hard drive has problems, I hope not because that would generate more expenses. Thanks for the information, I'll show it to my brother. Have a very happy day!
yes that should be even better to just replace the motherboard and processor or ur old computer! i guess u rely on such programs to run on windows so them raspberry pi would not be an option for u anyway.... for me windows is not an option ^_^