Hi S., I think I'm #47 to respond, but I have scanned the responses and what is missing is useful advice (as you'll see, everyone agrees that "close in age" has some truly blessed benefits in terms of companionship, independence, and being close to their siblings despite the natural bickering that will happen no matter what age). SO... Do not be discouraged by people who say "that will be hard"--try to understand it isn't a criticism, it is a comiseration with you, because they know IT IS TRUE! My two boys are 17.5 months apart, so I'm speaking from experience (and my youngest just turned 2 last month). There is little that is "very easy" during the first year of two kids so close in age. In fact, it is much like having twins (confirmed by my SIL and a friend who both have twins AND an older child). When you get that response, say, "You're probably right. Can I count on you to help me out in the beginning?" I'm betting people who are your friends will say YES. Remember, there is NOTHING wrong with asking for help, and believe me, any mom with two kids that close in age WILL need more help than she thinks, especially in the first six months, and doubly true if she's nursing (because no one else can do that job, LOL!). So line up people who are willing to come over and wash the dishes/laundry, run errands, take the older child for an hour or two so you can have 1:1 with the baby. Your life will be much easier and less stressful if you plan WAY ahead. Sit down with a calendar and figure out what you're going to do during week #3-4-5 after the baby is born, when your husband is back at work and the grandparents aren't around (unless they live close by). Schedule 2 days each week to have a friend or even a post-partum doula come in and help you, either with baby chores or household chores. Get a mother's helper (many towns have a youth & family services program or a job match program for kids of the baby sitting age--mother's helpers are usually a little on the younger side, but you only pay them $4-6 per hour) who will do simple tasks around the house to help you keep up with things.
I knew I was having a boy the second time around so I knew I could take advantage of hand-me-downs...only problem was, they were born in opposite seasons (winter & summer) so I still needed new things for #2. So get your fall/winter clothing concerns figured out now, and take advantage of your local www.freecycle.org Yahoo Group. It's a fabulous way to get (and get rid of!) FREE baby clothes/gear among thousands of other things.
Definitely make a big deal out of the older sibling's new role as "helper" and "big brother". They're a bit young now to understand much, but just wait, it'll sink in once baby arrives. We bought a "big brother" gift from the baby to our older son, so that he would feel special. It was a toy tool set, which we deliberately chose as something they could play with together as baby got older (and they do! Now they are 3.5 and 2.1 y.o.). Anything creative you can do to help your toddler understand the baby is not an intruder or usurper of your time and attention is all for the best.
Create a special backpack or basket full of items that your older son can only have access to whenever it's time to feed the baby. Prepare a sippy cup for your toddler so he has something to drink at the same time as baby. In the basket/backpack, include a dry snack (pack of Goldfish or fruit snacks), a Color Wonders book and markers (ink only works on that special paper), a musical or talking toy of some kind, two wooden puzzles, and a bunch of colored blocks. The idea is to get your son engaged in an activity he can do himself while you are focusing 80-90% on the baby. My son's favorite time to cause trouble (tipping over or pulling leaves off plants, getting into the food cupboards) was when I was sitting down to nurse.
Also, never tell you're older child "we're almost ready to go" unless you 100% mean it. I often had to take him to gym class or daycare, but suddenly realized the baby needed to nurse (I nursed on demand, not by schedule) and so had to drop everything to nurse. This infuriated my toddler, and rightly so, because I was talking without thinking, and not planning properly. So if you need to take DS #1 someplace, be sure to feed & change the baby 30 min. before you need to leave, not as you're heading out the door. That alone will reduce the stress of being a busy new mom!!
If your town has a babysitting coop, join it! It's a great way to get 1:1 time with each child while the other is off on a play date (coops operate on a point system instead of using cash). It also allows you and your husband to get 1:1 time without the kids around (once baby's old enough to be left w/someone else).
Oh, I almost forgot the most important thing. SLEEP! Go to bed ON TIME each night! That means by 10PM if at all possible. Do NOT do chores after you put the baby down for the night except to clean up after dinner (your day starts off best wtih a clean kitchen). Everything else can, and should, wait. I learned this the hard way, and I regret all the nights I stayed up doing email, folding laundry, paying bills, etc. A tired mom is a cranky mom, and moreso when she has a toddler and an infant. My toddler gave up his second nap the week before #2 was born. I was in crisis--I'd counted on his nap and it was GONE. To make matters worse, he also stopped sleeping through the night reliably, so for the first 5 months I did not sleep through the night even ONCE. I eventually coped by ensuring I got enough sleep at night and by tiring him out when the baby was awake, so that they would nap together at least once during the day. You know you'll be up for those night feedings for the first 5-6 months, so getting your toddler AND yourself to bed early, AND napping when the kids nap, is CRUCIAL.
Your job is to take care of the kids, not to be SuperWoman. Be sure to get your husband to understand that he also needs to make sacrifices, which may mean no Monday night football because he's the one who has to pick up some of the household chores. Hey, he can fold laundry in front of the tv, right? Enlist his agreement now to help out later, but it'll go best if he gets to choose the manner of helping (maybe he digs cooking & dishes over washing & folding). It takes two to raise a child, it takes two to make a house dirty, and it takes two to clean it up. Establishing good habits ("picking up after yourself") with your husband and son now will go a long way toward keeping from getting behind after the baby is born.
Yes, it IS hard, and I DO have my hands quite full with two boys that are <18 mos apart. Would I do it that way again? No, and it was a fluke that it happened this way. There have been many difficulties along the way, and my 3rd child is planned to arrive in 2 years or so. My 3 younger sibs are between 3.5 and 12 years younger than myself, so even my mom doesn't understand how hard it can be sometimes. BUT I have learned many valuable lessons, and I would NOT CHANGE the way it is. My boys are becoming very good lifelong friends, as #2 really worships #1 and thinks he's the same age, I swear. There are so many wonderful things about two kids so close in age, which most people have already mentioned below. But the comments you hear are not focused on the long run, they're only thinking about what you and your girlfriend face in the coming year. Remember, don't be discouraged by "that's gonna be tough"--instead, use it as an opportunity to ask for support, even if it amounts to someone bringing you a macaroni casserole for the freezer once a week.
Good luck!