How do I migrate everything from one recent Imac to another, temporarily.

I have an Imac running Yosemite, with all sorts of programs (Microsoft for MAC, dropbox, filemaker) photoshop, anti virus etc etc) but it needs to go off for repairs (the stand is broken). Fortunately, as its in a business theres an un-used very recent IMac (it doesnt have an Apple ID that I know of so it doesnt look like the Yosemite upgrade is going to work, but it has all the latest software).

This computer was being used by someone else & has various programs on it (including someone elses emails I need to keep) but not photoshop & the same Microsoft suite. Id like to move all of my programs, emails (I use Exchange/Outlook) & everything else to it while mine gets fixed but dont want to over write whats on there & have to buy new licenses etc.

When mine gets returned Id like to move it all back again. Is this possible? If so how do I do it? We are on a network but Im not sure I can access that computer from mine on the network. It doesnt matter how long it takes as I will simply keep using mine until the migration is complete. Ive got ipads, iphone & a home mac with my music is on those I dont really have that kind of stuff on my work computer but I do have my apple ID associated with it.

I can buy cables or whatever, I just want whats easiest, & works best! I dont use icloud etc.