I have applied to teach through Interac and they normally advise going with Leoplace.
Some accommodation places prefer to only deal with companies etc rather then individuals but nearly all places require key money and returnable deposit.

dont forget that these sites are also for the japanese and so because they are normally more trust worthy and respectful of the places they rent it maybe them who dont need to pay key money etc
This may seem slightly unfair and misleading but you have past westerners to thank for that