I have never done a houseshare, though I'm thinking about it too. But my mother and I shared with other single mothers when I was a kid. Those arrangements never worked out well, though that could be blamed on my mother's personality. I remember all of those housemates leaving in a frantic huff while my mother screamed at them in the driveway as they crammed boxes into their cars. Not good.
My mother is a nice person and seems like a nice person at first, but she sucks at conflict resolution. If you bring up a problem you have with her, she will immediately get really defensive and throw a tantrum like a toddler. So, if you're planning on sharing with another mom, try to ascertain how she will deal with conflict. It's hard to know until you actually get into a conflict, but inevitably, conflicts will arise and it will fall to both of you to resolve matters in a responsible way. Perhaps come up with a gameplan before hand, like, agree to resolve major impasses by email which tends to get less heated and personal than in-person arguments.
It's also really important to set up ground rules. Be thorough and try to get an agreement (maybe even in writing) about things that might come up.
One of my mom's housemates was an art student who would head off to her studio to work after her son went to sleep without checking with my mom. The boy would wake in the middle of the night in a panic looking for his mother. My mom was super uncomfortable with this, though it seems talking about childcare exchange in advance might prevent any discomfort or hard feelings.
I would want to be crystal clear on things like drugs/alcohol, hosting friends/lovers and visitors, housekeeping styles, etc... I also think it's important for each family to get space and not feel like they're constantly walking on eggshells as to not offend the other party. I think if I shared a house, I would try to set up a loose schedule where one family would clear out for a weekend every once in a while to give the other family free run of the house to play music, host a dinner party, lay on the couch in your underwear with take-out or whatever.
...Just my 2 cents.