My MIL does it (has done for 20 years) and I've looked into it.
It is HARD work especially considering the money. The provider MIL works for has lots of rules - eg. the kids have to paint every day (imagine doing that every day on your own with 4 toddlers under 2.5), no television to be on during the day at all, they have to go to the park at least once a week, she has to fully mop and sweep her whole house every morning before the kids come and she has spot checks at least every fortnight where they just show up without warning - there's heaps more but you get the idea. It's quite structured and full on and after looking into it I decided that I don't have the self discipline to do all that in my home every day, I would get too distracted with other things not to mention trying to clean up every night with my own kids still here.
If you want to be home with your kids its definitely an option but you really need to your research and find out what's expected. There is also alot to cover in terms of your own home, as someone said - safety etc.