1) Is it important to have a big room to train in
It's important that it be big enough for whatever we're doing. Sera is a close-in system. There doesn't have to be too much space per person. But it's nice if you're sparring, training with weapons, or doing up-and-back drills.
2) does the room need to be matted for you or at least carpet
For ground grappling and taking a lot of falls I don't need mats, but something like sand is welcome. Irregular ground, slopes and different materials are good. Taking dozens of falls or rolling for hours on concrete, rock or hard-packed ground gets old fast.
3) Do you need all the latest equipment to be productive with your traing
Nope. There is some equipment which is very nice. I lust after Phil Messina's school with its leg-breaking dummies, wind, rain, sound generators, and simulated environments. But I don't need anything like that. Some focus mitts or Thai pads, maybe a heavy bag, tape, a decent surface, practice weapons, shelter in bad weather, a CD player with a selection of appropriate music or a couple hand drums, and a heater for my wife to stand in front of in the Winter, and it's all good. Mouth guards, MMA gloves, cups (for the wimpy

) and a well-stocked first aid kit with plenty of Balur Silat are nice, but everyone should have his own supplies of these.
What else do you need?
4) In your mind is it a factor when choosen your school
All else being equal nice facilities are nice. But I haven't actually trained in a dedicated single-purpose school in quite a few years. It's just not necessary.