So I'm about one move ahead of you- just did my first bike commute yesterday (is it still a commute if it's to the bar??)

I'll just run you through how I went about getting started, having zero knowledge. Apologies if you have experience with bikes- I had done some racing and riding as a kid, but was just that- a rider. Not a real maintainer, fiddler, care-taker. I think a lot of people are likely in this position, but again sorry if this is too broken down for you. I struggled with my initial research because everybody assumed things were obvious that, to me, weren't in the slightest. A good image of a road bikes anatomy was endlessly useful to me.

I want to second the advice about considering accessory cost- it's considerable. I ended up picking up odd pet-sitting/babysitting jobs from care.com to fund my outfit (as a teacher, summer = no paycheck), which worked really well. Mine was higher than it should be because I was an idiot when buying...

I was in a rush to buy (car in the shop, needed to get to obligations), and hadn't really spent time with a bike in awhile, so was trying to deal with being unfamiliar with what I was looking at and considering look, feel, and condition of the bikes. I was seduced by a pretty frame, excellent condition, no rust, perfect paint, and, as I learned after purchase, completely shot tires. They had been run over with shoe-black to disguise the wear. I was nervous, in a rush, and not confident with what I was looking at/for. My fault, so I'm not terribly mad about it, I'm kind of a pushover, plus I'm already 100% in love with my 1982 peugeot p18 mixte. (I also had to buy new brake shoes, about five dollars each so not a huge deal..). At least in my area, there are a good number of good to great condition 80s road bikes for $100-200. Just be more careful than I was!

I would recommend, if you can, that you borrow a friends bike and just kind of look it over and see how it works, how adjustments would be done, etc. This morning I centered my tires between my brake shoes, adjusted my rear rack, removed a spoke reflector that had a broken plastic piece, thus dangerous- if it slips and catches in the spokes = me on the pavement, and learned my quick release tire mechanisms. I already feel far more confident with the machine- and it honestly was a lot of fun. I almost wish there was more wrong on her to mess with! (I can just hear people cringing...)

So my bike was a craigslist purchase, obviously with mixed results. I did manage to correctly assess everything else about the bike- no rust on the frame, very minimal to none on any components, good fit for my size, light-enough-for-me-frame (I've only ridden mountain and old, cheap, clunky steel frame road bikes in the past, so my steel carbolite frame feels to me a breeze, though I'm sure many out there are scoffing! will be a bit sturdier than a super-light road bike as well, I think anyways), plus smooth shifting that was in a comfortable position for me (older bikes often have shifters on the downstem (tube between handlebars and front tire, perpendicular to the road) and I wanted them where my hands were already resting). A 12-speed is plenty for me, I rarely shift the big sprocket from the harder gear (sorry for my lingo, gear vocabulary is still being learned).

I looked around for a hybrid too, but roads were just cheaper and easier to find. The streets where I am aren't great, but potholes are far easier to swing around on a bike than in a car, I found (duh I suppose.) The bike I chose does not have dropped handlebars- I wanted these initially, but the position was just too forward-heavy for my purposes. I'm not racing, not going too far, and wanted to be more comfortable/upright.

Back to accessories... I would highly recommend a rear rack and pannier over a backpack, especially with your distance. Personal choice of course, but I went out with a shoulder bag last night and was not happy. Ended up pulling off to bungee it down to my rear rack after maybe half a mile. I was able to get my seller to throw in a rear rack with the bike (thank goodness, offset my tire goof a bit.) It won't last forever, but I tend to spend a little more to make one quality purchase, so I'm hoping it'll at least give me time to see a few more paychecks before investing in a long-term/lifetime quality rack.

Locks were my biggest concern. My childhood bike was stolen almost three years ago, and I'm just now getting around to replacing it and becoming a true bike commuter. This is a pretty bad bike theft area. To me, spending for secure locks was worth it- they last forever if not taken to with power tools, and besides the money, finding a new bike is a huge hassle, not to mention sentimental value once you've put time and work into making it yours.

So I got two locks. I went with a Kryptonite New York Standard U-lock- $63 from powersportparts.net. Box was a bit damaged on arrival, but it's a heavy lock and was fine. Logo is a bit funny on one side, but I didn't buy it for looks. Arrived extremely quickly. This is for my rear wheel and frame. Provided you are locking to a rack and not a thick pole, it will be large enough for two bikes (I'll get back to this in a second..). My second lock I went with a Hiplok lite- a wearable chain lock covered in fabric. Found it for about $40 I believe. Comfortable on my ride last night strapped around my waist. This is for my front wheel. A combo like this means a thief will have to have two different, and fairly heavy, tools to get my bike. (No locks are unbreakable.)

If either you or your gf can take your bike into work, this combo could serve you well, as both locks are large enough to securely lock two bikes when you go out together. If one can take bike into workplace, or if you both are in safe areas, you could save money by sharing the locks for your work commutes. My concern for theft is not from my workplace, but from errands and evenings out, so I made sure my locks were big enough for my boyfriends bike too (his bike is just is a garage sitting play bike, he had no need for locks of his own.) I hope that make sense.

Sorry this is getting long, I'll just give you my starter gear list. Again, I like to one-time buy:

-Cygolite dash headlight: $40 (don't forget to remove and take with you when you are leaving your bike!! Way too easy to steal.)
-Cygolite hotshot rear light: $20
(Both multi-mode, USB recharge; I affixed the rear light to the back of my helmet- higher up so more visible, plus one less thing to take off the bike on arrival. Cars gave plenty of berth last night, so I'm content with these choices.)
-Specialized helmet: $30
-Bungee cords: $3
-2 extra tubes, wheel levers: $15
-Dry chain lube: $5
-Air chuck elite (co2 pump for emergency flats): $20, refill tubes $3.50
-Floor pump, I got the STX Deluxe from REI, $45 (there are cheaper but the cyclist helping me said you get what you pay for, and this was the cheapest model worth the money)
-Crank Bros 5 multitool: $10 (picked this up today, after my rear rack needed adjusting on the road last night and I had to reshoulder my uncomfortable pack to keep the rack from rubbing the rear wheel)
-Vaude Cycle 28 pannier/rucksack: $128 from bikebagshop.com (hasn't arrived yet, so I can't yet speak for this purchase. Chose after extensive research, wanted a large pannier that converted to a rucksack so I could easily grab it off and carry into work/the store. You don't ever want to leave anything on your bike, so I liked how this one had many pockets- many keep their repair tubes and tools in a small frame bag, but I will just keep mine organized in this larger bag, as it will always be going with me and, again, one less thing to remember to remove/carry with me on arrival. Hoping it will prove large enough for a gallon of milk and a few other groceries. This was the hardest purchase to choose/swallow, but again hoping this will be a one-off for a looooonng time, and after learning last night I hate riding with a backpack or messenger bag actually on my back, I'm glad I got it, pending arrival and testing it out of course.)

As you can see, it's a considerable list for what you need to be safe and comfortable in any situations while riding. I'm a canoer, so I have a small drybag I plan to keep with me for my cell phone in case of bad weather. I hope to eventually purchase a J&G breathable rain jacket, but I'm waiting on that and will just get wet/wear my regular rain coat in the meantime. I already had a pair of Pearl gloves and two pairs of padded cycling shorts (which I will be wearing if I go much further than last nights 3.8 mile each way commute- I just wore street clothes and don't have a great saddle, I will likely upgrade eventually- call me a baby, but my butt was already sore!)

I hope this helps! And I hope I'm not scaring you away. There are definitely many other ways/ gear choices, etc, this is just what I have been doing as a new commuter. After one ride, I'm hooked, and already really enjoy maintaining and tinkering with my new "car". Good luck!