I think the cost efficiency of growing your own food will depend greatly on your current diet.
Not saying you eat like this, but if you eat a lot of processed food, or industrially grown bulk foods, then it's going to be hard to compete with empty calories, government subsidies, and cheap imports from third world countries. This is especially the case if you're planning on creating a farm scenario that is effectively a micro version of industrial farms. Industrial farms are only successful in growing food by virtue of scale and the cheapness of bulk chemicals. Try to replicate that system on a small scale and the inputs cost far more than the outputs.
Self sustainability (or something relatively close to it) really only works at its best when you address the whole system. A few examples:
Grey water from your house can water your fruit and nut trees. Reuse water you're already paying for, rather than let it wash away into the ocean (where synthetic clothing fibres from washing machines are causing a bigger problem than microbeads *cough*derail*cough*).Black water, organic waste, and noxious weeds with viable seeds can enter a worm septic system that creates compost and worm tea for your gardens. No compost bills.Earthworks captures water that falls on your property, replenishing aquifers, creating dams, and creating ponds. This water is used to passively or actively water crops and animals. No water bills.Proper rotation of animals on pasture creates pasture where nothing but eroded, dead dirt was before. 100% pasture-fed animals turn hands-off, inedible plants into high protein, high fat, nutritious food for us. If done properly, you can get far more protein per acre than any other system (refer to talks by Gabe Brown, Mark Shepard, Allan Savory, etc). Even on a small scale, you're creating your own food AND the animals fertilise your paddocks for you so you can continue growing plant food for them and yourself. Close the loop.Growing your crops (trees or otherwise) as part of a silvopasture system means you're capturing solar energy at all levels, producing annual crops (animal or plants) while perennials mature, and providing shade and shelter for animals (which boosts weight-gain and health). This is a much more efficient method of producing food than industrial ag's monocultures that require ample inputs to compensate for the deficiencies in design. Good design is important if you want to save money.
You'll save money very quickly if you already have an expensive diet. This is a big deal for me, because organic food is very expensive here in Australia, and that food is usually not very fresh, and not even particularly nutrient-dense. A couple examples:
Growing my own garlic for the year takes very little effort. A handful of seed bulbs ideal for my area are a one-off purchase, because I save my own bulbs for next year's planting. At harvest time, I get all the garlic I need, for nothing but a little labour. Alternatively, the shop sells fresh organic garlic at $50-$80/kg.While growing my own chillis takes more effort in my area (fruit fly, birds, and fruit worm all love my chillis, and thanks to pest-ridden neighbours, they're hard to get on top of), a few healthy bushes produce enough chillis to keep me going for the year if I fridge pickle them. Compare with $34/kg for NON-organic pickled chilli with additives.Even on my small suburban block, my chickens provide me with meat (when a rooster hatches), compost, weed-eating, and very nutritious, super fresh eggs. I feed them scraps, garden waste, and some organic feed. To buy organic eggs at the shop, I'm looking at $8-$12 per dozen, and they're already up to a week old. My organic eggs that were just laid this morning work out to be $1 per dozen, because my small backyard won't support 100% pastured poultry. Still a big saving. Not to mention the fact frozen organic chicken meat costs upwards of $25/kg. So my roosters save me money too.
A big question for you- do you enjoy gardening at all? My sister loves good quality food, but hates gardening. She thought she could grow her own food with purely savings and quality as motivators. She didn't last half a season. Even the most laid-back of farming systems require some work. For my sister, what I considered "practically no work at all" was too much work for her, because she got zero enjoyment from the process.
The smaller your land, the more intensive your growing systems need to be, which means more labour creating that system. If your diet relies a lot on foods that can't be preserved, your labour increases, because successional plantings are needed.
My two cents, from a newbie.
I've been looking at various smartphone apps for doing my plotting on the ground. There are many out there to choose from, and I cannot yet speak to which work for this kind of thing. Give me another couple of months and I'll have more to say about it, as we work to lay out our homestead.
I'm tempted to factor hiring professionals into the cost of purchasing my land. I've got my eye on services like what Darren Doherty's mob provides. They take care of mapping as well as the actual earthworks, from what I can see. It depends how easy/cost-effective/non-disastrous it would be for a newbie to pick up. 
My climate is different to yours, so I can't comment too much on specific plants. I was absolutely amazed how bonkers my rhubarb grew with zero tlc. Broad beans, runner strawberries, herbs, and garlic are also way up there with my most successful newbie plants. I literally did nothing but plant them and water when things got dry for too long.
