Hi welcome to the forum!

Short and sweet:

A machine designed to run a plasma torch doesn't need to be anything overly sophisticated or substantial in design, providing you build the machine mechanically sound i.e all axis's run smooth, free of binding and square to each other, a simple design using somewhat "light weight" materials can be used to build a nice machine, this lends well to not needing such things as big powerful motor's.

Have a look in the build log section Plasma Table Machines, here you can see what others have built in the build log section, I'd say more importantly would be to read through some of the other non build log discussions as running a plasma can be troublesome in other ways (electrical noise etc.)

As time is against you, it maybe a better option to look at a commercial machine such as the Blue Marlin from Techserv, "I would like to build a machine" and "but I dont have the time" dont really go well together when it come's to any type of CNC machine unfortunately, so if you really do want to build your own, the minimum investment is going to require a reasonable amount of time just on the discovery of the components you'll be working with.

Spending the time you do have in a commercial machine and so the company, would come with the benefit of (I would hope) support at the end of the phone if and when you need it, as although you'll get all the help and support you need from others on the forum, a request for help here isn't guaranteed or a response time.

.Me