"Abs are made in the kitchen."
Basically, to have visible abs (and any muscle, really) you need to drop your bodyfat. Your actual body fat and muscle mass will get you those abs. For example, you may have a well defined six-pack, but a layer of fat may be above it. Or you may have very little fat, but no abs muscles. I think you get my point.
So basically, lowering your body fat and getting visible abs is more than just running 2k and doing 300 situps everyday. THAT DOESN'T WORKS.
What you need is a nice diet, complemented with resistance training (weights, basically) and some cardio. To start burning fat you need a mild calorie deficit, and this process takes a while, from 4 weeks to 16 or even more, depending on your current body fat.
As for your diet, you need to eat 5 to 6 small, healthy, frequent meals (leave 2-4 hours between every meal), all which need some sort of protein. Keep yourself hydrated, drink AT LEAST 2 liters of water everyday. Keep away of junk food (refined sugar, refined flour, sodas, sports drinks, alcohol, energy drinks, potato chips, candy, fast food, etc). Stick to good sources of protein, such as eggs, chicken/turkey breast, fish (salmon, tuna, etc), cottage cheese, milk, lean cuts of meat (sirloin), WHEY, soy, etc. Also, stick to complex carbs, such as oats, brown/wild/integral rice, integral pasta, sweet potatoes, etc, and only use simple carbs after workout (dextrose, maltodextrin). Fruits are ok, you can have as much as 3 pieces per day. Eat vegetables in abundance (except for potatoes). For fats, they must compromise 20% of your total calorie intake, stick to the good fats: olive oil, avocado, salmon & salmon oil, flaxseed and flax oil, nuts, almonds.
For your training, you don't need to be on a gym, but it's highly recommended. A good routine needs to use every muscle at least once per week. Do not abuse your abs, train them like any other muscle, once or twice per week should be enough.
Do these workouts until you can afford a gym:
http://www.trainforstrength.com/workouts.shtmlFor cardio, 30-40 minutes 3 times per week should be enough. If suddenly you feel 30 minutes aren't enough, push the resistance up: run faster, run uphill, whatever. Intensity is everything. Also, you could try interval training, that burns even more fat.
Lastly, genetics do play an important role on your muscle mass and definition, but EVERYONE can get a six-pack. Check this site, is really useful:
http://www.iwantsixpackabs.com/Hope this helps man.