It’s easy to get carried away and bring in all the eggs you can find. If this is your first rodeo, I can not recommend strongly enough that you DO NOT DO THIS:
For one thing, unless you have a field of milkweed (I do.), you will likely end up starving many of them and that will be just awful, for you and for the caterpillars. Expect to need one 4-foot tall milkweed plant for one caterpillar. FOUR 2-foot tall milkweed plants will do, too. Not two 2-foot tall plants! It won’t be enough, because the amount of milkweed doesn’t translate by height in feet. Taller plants have larger leaves.
If you’d like to try raising Monarchs, I recommend bringing in three eggs for your first foray if you have enough milkweed for that many. You may end up with three butterflies, but you will almost certainly end up with at least one and you won’t be overwhelmed by the amount of time and effort it takes to feed and care for them.
I’ve been doing this for close to two decades, I’m very efficient with my feeding and cleaning of containers, and when the caterpillars in the photo above get big it will still take me an hour and a half every day for a week to keep them fed. It would likely take a butterfly newbie four or five hours a day. Do not do this to yourself. Please. It will not turn out well.