Selling chicks shouldn't be too difficult. Make sure you hatch pure breeds though, as they will be easier to sell than mixed breeds. Also look around to see which breeds are very popular, like Easter Eggers for example and if you can find hatching eggs from show quality breeding stock even better.
Incubating and hatching eggs is not very difficult, provided you have proper equipment and sticks to the guidelines. First of all make sure your incubator works as it should. Let it run at least 24 hours and keep an eye on the temperature and humidity. If those 2 are not correct it could ruin your hatch. Too high temperatures cause early hatches, can cause foot and leg problems and even kill your embryos, too low can delay your hatch and produce weaker chicks.
Your eggs should be as fresh as possible for the most successful hatch. Preferably not older than 7 days. Use only clean, well shaped eggs, no weird shaped shells or porous eggs (they can be very tricky to hatch). Look for intact shells, intact air sacs (not always a guarantee with shipped eggs, but you can work around that). Keep your temperature correct and stable, no highs and lows and keep your humidity correct at all times. Turn the eggs minimum 3 times a day, more is better, and you should be successful.
 
Here's an excellent article with loads of good tips on incubating, managing air sac damage, how to get the most out of shipped eggs etc:
 
https://www.backyardchickens.com/a/hatching-eggs-101
 
Good luck with your hatch(es) and keep us posted!