You didn't state what your schedule looks like (unless I missed it). If you never know what time you'll get home, then cooking pretty much isn't for you, unfortunately. But if you get home at the same time every night, then there's really no excuse, save laziness, to prevent you from cooking.
TONS of great tips/advice in the replies; some of them I would've posted too.
Being that you're single, your schedule dictates how much time you have for cooking. Trust me when I say that eating healthy NOW will dictate how much work you have to do later in order to stay in shape. In my 20's I worked 12 hours a day, then partied until way after midnight, then ate whatever fast food I could buy at 2:00AM and got up at 6:00AM to do it all over again. I never gained any weight until about 34 year old and THEN...all that weight just dropped on me like...a fatass deferred, or something.
I've had to work very hard to lose the weight and KEEP IT OFF. Eat well NOW and it will help you later. And later WILL come.
Eating healthier is the main motivator. My Dad gained a ton of weight in his late 30s and I want to avoid that at all costs.
Generally I get home at a set time so I should be able to find time to cook. The plan right is to develop a monthly schedule of meals with the info posted above. If I don't follow a plan I know I'll have problems following through.
Just ordered the cast iron skillet and slow cooker from amazon and can't wait to try them out.