I'm just getting into using number of cheap server racks. I look into rack consoles and they look pricey for this particular work I'm doing. Do you know if I can turn my old MacBook Pro (early 2011) into one?
Just a guess here but it sounds like he wants to use an old MacBook as a glorified KVM. Now Server rack KVMs have a connector that goes to the Keyboard, Mouse and Video port of every server.
To do something like this you would need a software controllable KVM switch as you cant plug all of those servers into your MacBook and switch between them without some sort of hardware. Even then I'm not sure you can view incoming video, I am inclined to think not but am not completely sure.
One thing you MIGHT be able to do is use RDP and/or VNC on the MacBook and then plug the MacBook into a small dedicated hub/switch that then goes to a "spare" ethernet port on your servers.
Most servers have multiple ethernet ports and dedicating one to a "soft KVM" might work if they are not otherwise occupied.
The problem with that is that it is not strictly a KVM as it depends on the server's O/S being up and running, where a true KVM is nothing but a switch that connects directly to the server's keyboard, mouse and video ports. Allowing you to see and control the system from power on to power off, BIOS and other non O/S status messages included.
So for the TL;DR summary, probably not