we have had only one helper since both of my children were born. she may not do things EXACTLY as i would, but then again, neither would my husband. my kids adore her and she loves them, too.
we've never had an issue with "safety". i have always made it mandatory that my kids leave the house at least once per day, be it for a walk, a jump on the neighbourhood trampoline, a trip to the supermarket etc.
expenses:
$3580/month (minimum salary)
$740/month (minimum food allowance IF she doesn't eat the same food as you, if she eats your food, then nothing.)
$500/year insurance
one trip home at the end of the contract ($ depends on where they are from)
personally, i LOVE that my kids are not numbers in a daycare and that they get really personal attention. my helper is very good, though at not raising "babies". my kids are VERY independent and LOVE to do things "by themselves".