Hrm

Well, I don't think there is anything wrong with having only one, and I don't think it's selfish BUT I also think the reasons you talk about are kinda irrelivant....
Take cost for example....people talk about that ALLLLL the time and I just laugh. My first was unexpected. I was not in a position financially at all. BUT...you make it work. Every family does. I have yet to meet a loving family who has one child who just doesn't get clothes or food, ykwim??? Lets just say you guys got preg next month and decided to go with it....you'd make it work. Things might be a little tough in the begining but you'd make it work. Everyone does. And I think that maybe it's a little easier to work another into the budget when you've done it once or twice. And, personally, the notion that a baby is a "burden" in this way leaves a sour taste in my mouth. Sure, I don't go out to eat as much and I am not the fashion maven I was when I was just me...but I also don't CARE about those things as much....just as your costs change, your priorities change. I think thats why today you see so many mamas changing to a voluntary simplicity plan...because it's easy to do because you love your kids. I'd rather stay home with my dd any night of the week, cook us all a meal, and cuddle on the couch.
And giving your time to another.....I DO NOT wish this to sound condesending.....I think this issue changes over time. I think that now, I can TOTALLY understand you saying that. I may have said it myself when my dd was that small of a baby. I'm preg now with #2 and dd will be 5 when he/she comes and I'm thrilled for us with that spacing..........I got to spend dd's baby years with JUST HER and I wouldn't have traded that for the world, personally. And, now she's so independant and she'll be starting school shortly after the babe comes....and I'm lucky enough to be a SAHM and I'll get all THAT baby time with THIS one too!!! What I'm trying to say is that maybe it's just something for you to revisit in a few years when you've been a mama longer and your baby starts really coming into their own. And who knows...maybe at that time you'll STILL want an only, but know that sometimes, for some women, that feeling changes once your baby isn't a baby anymore.
I am one of two myself, and I never felt like my fathers time was split between me and my brother. I also don't feel like he loves one of us more or less than the other. I think the heart of a parent is made of infinite stuff that can hold just the right ammount of love it needs to. And thats the important part. I know of so many moms who worried about "not loving the new one as much" and they all said that somehow it worked once that new one was there. Sure, maybe they'll have to share a room or whatnot but the love is the important part....the other stuff is just part in parcel with being in a family.

All that said....again, I personally don't find anything wrong with people who want to have onlies....I think only kids have just as many "weird hang ups" as kids with siblings. People are people. And, if today or down the road this is the choice you make for your family, then I wouldn't worry. It just shows what a good caring mama you are to be worrying so much about it now, you know?