Being a home carer or home educator as they are sometimes called is a great idea.
you can have a max of 4 children under 5 in your care at any time. so you can have three as you have Ethan. You can earn about $4 or $5 per hour per child.
You do need to have a play space lounge is fine as long as there is enough room for children to play . must have and toys and equipment.
Outdoor area is essential room to kick a ball or run if not having a park close by is great.
joining the local toy library is a good option then you have different toys for the children to play with.
The advantages of going through a company or organinstion is they find you children and do the parent contract (porse is a bit different check their website) also they take the money and pay you so you are self employed and are contracted to them. The tax is low as well and IRD send you a tax bill at the end of the year.
plus a qualifed ECE teacher will visit you and help you with play ideas, educational stuff and support and guidance.
Look around there are a few home based care groups out there offering different things.
It's a great option if you love kids!

Good luck !