Just to second (third? fourth?) the 'you don't need suspension' replies. Too much suspension and knobbly tyres will make it harder to ride, and sap your energy. Think of the difference between running on hard sand and soft sand on a beach - it's much easier and faster on hard.
Ideally a commuting bike (for me, anyway) ought to have fairly slick tyres, no suspension, mudguards, to cut down on the spray both onto yourself and onto anyone behind you, and a rack, so that you can carry what you need to off your back. But plenty of people manage without these, and use a rucksack or courier bag.
Also, if you are budgeting a certain amount of outlay on a bike, bear in mind the extras you'll need
Lock. A good one, like a D-lock. A rule of thumb is to spend 10% of the value of the bike on a lock.
Pump/puncture repair kit/spare tube. If you don't carry them, you're guaranteed to need them.
(Acting on this principle, I carry about half my bodyweight in 'essentials' to ward off the evil eye, but I'm a bit of an extreme...)
Perhaps a suitable waterproof and breathable jacket. Hi-vis or not is up to you, but a jacket that fits right and isn't too stuffy really helps.
If you haven't cycled on the roads for a while, buy or borrow a copy of Cyclecraft, by John Franklin. This book is the how-to bible of modern transport cycling, telling you all about how to claim your space on the road, maximise your safety, deal with hazards etc. Many of us think it should be compulsory reading! And to go with it, perhaps, a copy of the new Highway Code edition (or look online).
And if you choose to, a helmet. Again, debatable and there isn't room to go into it all here, but if you get one, make sure it fits properly and you know how it should be worn. Seriously, you'd be amazed at the number you see worn backwards...
Once you get hooked (no ifs!), there's padded this, hi-tech that, upgrades...
But it's quite possible to commute a decent distance in ordinary clothes, so don't feel you have to have 'all the gear'.
And enjoy it! Might be a good idea to do a couple of trial runs, at the weekend to familiarise yourself with the route when you have plenty of time. Not just so that you don't get lost, but also to identify tricky junctions, bad potholes etc.
And you can always ask us lot about stuff - here or in 'commuting'. We're mostly friendly, and we love to see another bod on a bike!