You would either be looking to buy an incubator or perhaps a broody hen
The hen option is certainly worth considering as she will also look after the chicks for you, providing warmth and protection along with teaching them how to be chickens
If you are looking for an incubator, I have to say the Rcom range are brilliant machines. They are so unbelievably easy to operate and all you need to do is fill the water up every few days, it literally does everything else for you !! The chicks will need heat for the first 3-5 weeks depending on the weather and their development via a heat lamp or electric hen but are fairly simply to rear. I don't think in all honesty that you would be able to make a profit from hatching such small numbers as cockerals can not even be given away down here and even hens are not selling as well as they used to.
The only problem I find with hatching your own is the amount of cockerals you get and unless you have a breed that can be sexed at birth you won't often know for 4-6 weeks for sure which are which
I think if you are just wanting a few laying hens you would be better to buy in some POL pullets if you can although you have said you are having trouble sourcing any.