I can totally feel you on this, man, because I remember what it was like to be broke and unable to do what I knew I needed to when it came to maintaining my body.
The two most important things to avoid are partially hydrogenated vegetable oil (trans fat/margarine) and high fructose corn syrup. Read the ingredients of everything you put into your mouth and if you see either of those two, eliminate it from your diet. Minimize sugar intake while maximizing protein. Eat foods with lots of fiber and drink plenty of water (this causes the fiber to swell in your stomach and makes you feel full longer).
The truth is, you probably CAN eat 6-7 times a day, you just have to pick cheap, healthy foods. SPAM, eggs, canned tuna and chicken, fruits & vegetables, all-natural peanut butter, whole wheat bread ... all of these things are good for you, inexpensive, and will make you feel full longer than eating a bunch of junk.
When it comes to exercises, just do bodyweight training, i.e., pushups, pullups, bodyweight squats, burpees, situps, V-ups, etc. etc. Check out some of the workouts on
http://www.crossfit.com for a few ideas and videos of the exercises being performed.
Also, have sex with your girlfriend more often. It's an established fact that you burn 360 calories for every hour of sex ... not a bad trade-off if you ask me
Your boy,
870