Keto is a diet that has been around a while, 1940's or so. The basics are you figure out how much protein you body needs to live and eat that every day. This is roughly 1/3 gram per pound of lean body weight. There are tons of calculators out there to determine that, but a doctor visit is the best way. Next, you eat fats to meat you caloric intake requirements. For most of us, that is 2000 calories a day. When I started I was hitting 1200-1500 a day and was not hungry at all; my doc said at the time that I was converting stored fat to energy, and this is when I lost the most weight per month. Then you eat very few carbs. Carbs are starches like you find in breads, grains, root veggies (Potatoes, turnips carrots etc) sugars of all types and if you are a purist, artificial sweeteners. You get you micro nutrients from dark greens like Romain, spinach, broccoli etc, and I eat a TON of olive oil to increase my fat macro ratios.

I dropped soda for coffee and feel better, but I was never one of those people who had bad reactions to the diet sodas I drank. Coffee is cheaper as well so there is that.

Rural food in the US, well it sucks. I'm right there with you. I learned to love the omelet and consider myself a master at them now. Eggs are cheap and east to change around (Hard boiled so you can eat them quickly if you get hungry for example.) Find a butcher and see if you can get cheap bacon, or sausages, and cheaper cuts of beef. The cheaper cuts tend to have more fat on them, and the extra bonus of working well in a crock-pot so you can make a big pot of food and utilize leftovers to save money.

The short easy answer is that if it comes in an individual serving size, or is an "Instant" food, it is not low carb. If you have to eat at a hamburger place, don't eat the bun, no fries, etc. Condiments like the mustard and ketchup are loaded with corn syrups and sugars. If you can find a mustard with no added sugar get some and you will not regret it. (Yea I hate telling people to buy stuff, sorry but hopefully if/when you do buy things they will be worth it) And watch the salads; Apple-bee's puts a crap ton of sugar in all its salads. I'm at the point that I can't eat them, so those few times I go out I get the deep fried cheese stick, then eat a salad with olive oil at home to balance it out. The only fast food place that I like anymore is Whataburger and Steak and Shake. Both places have "not expensive" food and Whataburger will let you do bunless as an ordering option.

If you can swing a book, either library or Amazon, this is where i suggest you start. http://www.amazon.com/dp/1400033462/ref=cm_sw_r_tw_dp_9XI.ub1YHHVC6

I'm a lot better with things once I know and understand the WHY components of what I am doing. There are people out there saying that sugar causes Alzheimer's and cancer and crazy stuff, but I don't buy it myself. Sugar makes us fat, and that is fairly well established at this point.

Budgeting is hard. been there, done the whole live in shitty apartments paycheck to paycheck thing. MyFitnessPal is free and I've used that in the past (I now use a google docs spreadsheet). You live in a rural area, so find the farmer's market. Go near the time it ends and don't be afraid to haggle. Make friends with the farmers, even if only to say hello to them. Farmer's markets out here do EFT and Food Stamps now, so check that out as well.

Good luck and don't be afraid to ask questions.