Is this even an option?

My mom has brought an option up to me quite a few times...and I've thought of it myself over the last year. Every time it's brought up we both say it just wouldn't work...and I really don't think it would. But I'm really interested to hear opinions on this subject, so I thought I'd throw it out there.

My mom and I are best friends. I mean I she is really and truly the one person that I'm almost always in the mood to hang out with. We've always been best friends, even when I was a little girl. My parents separated when I was a year old and divorced when I was about three. My mom has always been my one person I can count on through thick and thin. We're so much alike it's scary. We don't even have to talk sometimes, because we're almost always thinking the same thing. She knows when I'm going to call her (we talk on the phone multiple times daily, to the point that my husband jokes about it) and she knows when something's wrong with me before I have even talked to her that day. Thursday night before she went to bed something told her to plug her phone in (she usually unplugs it at night so nobody will wake her up). So when I called her at 3:30am she answered on the first ring and wasn't surprised at what I told her. She's at my house about 5 days of the week. We cook dinner together, go grocery shopping together, hang out on the weekends together. She loves Hailey to pieces. She's the 3rd part to our little circle now. So we keep saying it's silly for my mom to have her own place, a job she doesn't like and us to have to pay for Hailey to be in daycare when my mom would be more than happy to stay home and care for her. We keep saying if she would quit her day job and move in with us, we could 1. afford a bigger/nicer place to live because we'd be $500 a month richer for not having to pay daycare and 2. we would never have to worry what we were going to do with Hailey when she's sick. Dan and I could both keep working, we could afford a house, afford to have another kid. But...my mom and I fought really bad when we lived together. We each needed our own space. Even now, if we spend a little too much time together in a week, we start to bicker a bit. Would it ever work, all living together under one roof? I know other people that do it. My sister in law's mother lives with them and watches my nephew while they're at work. My stepmom lives with my step sister and her kids. I know other races do it a lot too, esp. Mexican and Asian families. It's common in their culture. My husband wouldn't mind. He gets along great with my mom. If we found a place that was big enough, that had separate levels to where we could still each have our own space...would this be such a bad thing? Our fear is, we'd move in together to try it out, not get along, and 1. my mom would be out her wonderful townhouse that is cheap in rent but in a good area and 2. we'd be stuck in a lease on a place we can't afford. I mean to start off she'd keep working and we'd keep Hailey in daycare. We'd just see if living together would even work. But also I worry about my kids getting too attached to my mom. Or the other way around. We lived with my grandma when I was little and I loved it. I never saw her as my mom, just like a "second mom" sort of. I had different relationships with my mom and my grandma. I'm sort of just putting my thoughts down on "paper" here. Does anybody have any thoughts on this sort of thing?