I converted my garage into a home theater a few years ago and ran 4 breakers for it. I also wired my shop with 2 120v breakers and a 240v breaker. I learned how to do this correctly and to code by using the proper resources and calculations for which sized breakers I should be using. I will also be running 240v breaker and a dedicated 120v to the room where I'll be setting up my new grow. I'll be mounting my gang boxes and outlets in the ceiling via the attic instead of fishing romex through the walls. This, to me, is a better alternative.
This is fairly easy to do but it's also a very easy to get yourself killed if you don't know exactly what you are doing. Also, from what I understand, if you have a fire and your insurance company finds out your wiring wasn't done by a licensed electrician, your insurance may be denied. I'm not totally sure about this but that's what I hear.
These are the things I learned while working on my electrical stuff...
Don't get your electrical advice from a marijuana forum, go to an electricians forum.
Do not smoke and play with electricity (duh)
Before you do ANY work, turn off your main breaker and make absolutely sure it is off. A simple, but effective method is walking through your house and making sure nothing has power
Learn how to do EVERYTHING according to code and then bribe an electrician to inspect, make corrections, and sign off on your work with a little trade after you're done
Figure out the draw per circuit and mount the proper amperage breaker. Don't just put a huge breaker in your panel and run a whole bunch of power hungry equipment off it
Modern homes are using AFCI breakers for the bedrooms. If swapping out an AFCI breaker, swap with a higher amperage AFCI breaker, not a standard breaker. Don't take shortcuts.
A 240v breaker is nothing but a double 120v that takes up two spaces in your breaker box. It's not complex.
Don't have exposed romex running down your walls. Run your wires through your walls. Learn how to cut your drywall, fish wires through, mount gang boxes, and patch drywall.
If your running wires through electrical pvc outside, make sure you run TNNT and check the max amount of wires you can run through the pvc diameter pipes you'll be using
240v equipment uses the same amount of electricity as 120v but at half the amperage
Finally, if you don't understand how electricity works or you are least bit nervous about what you are doing, DON'T! You need to know what you're doing or there's a very good chance you will kill yourself or burn down your house and kill others. You need to have the confidence that you understand exactly how things work with electricity.
Hey people, be safe. It's so easy to kill yourself doing this kind of stuff.