Specifically I'd like to know:
* Rough cost per month to feed
* Can you let it roam around the house (eg will it remember how to get back to its aquarium(s)
* Lifespan in captivity (in the ocean they usually live 5 or 6 years.)
* Would toddlers be able to hurt it?
-I'm not sure on cost, but for this one and the lifespan in captivity question I'd recommend looking through the forums on Tonmo.com (a cephalopod oriented forum like Reef2Reef is oriented towards reef tanks). This species was a lot more popular in captivity ~10 years ago, so the threads on it are likely going to be pretty old, but I know they have few that may have some good information for you. That said, you can buy or breed ghost/grass shrimp to feed relatively cheaply.
-You probably can, but I wouldn't recommend it both for the animal's safety, and for others' safety as well (many octopus owners have been bitten - it's not a rare occurrence - and some octopus bites are venomous/particularly painful; some cephalopods may have toxic ink as well). If you want it to be able to wander around on dry ground, I'd recommend some sort of paludarium or tortoise table type setup (part marine aquarium, part terrarium).
-I'm actually not sure how long these guys live in captivity - I can't even seem to find a source mentioning how long they live in the wild - but, as mentioned above, Tonmo may have some info on this.
-Toddlers and animals generally do not mix well, and this particular combo is not one I would recommend as there's a good chance the toddler could hurt the octopus, and the octopus could hurt the toddler. As mentioned above, octopuses bite, and this specific octopus also inks, "punches"/whips and grapples with it's legs defensively, and may even autotomize its legs (meaning it might literally drop a leg if it feels threatened enough). Quite frankly, there's a very real chance that either the octopus, the toddler, or both could be seriously injured if they interacted. There's a chance they'd be fine together, but it's not a chance I'd personally take or suggest taking.
