Just looked online. The second socket looks to be for a spool gun.Anyone know about these? There's one local for sale for £50. It seems to have two torch sockets on the front panel. I've never seen that before.
The 2500 is 3-phase so it won't run on a normal household/shed supply.
The 2nd socket is for a spool gun but you can run a wire feeder from it if you like.
3ph is fine. I just wondered if they have any common problems that render them scrap. Probably worth a punt at £50.