Yes, you can get most fruits and vegetables just about any time of the year… but at much higher prices out of season. This is problem if your definition of “healthy” includes just the lean meats and salads.
But there’s more to eating healthy than just salad. And there are ways to economize both money and time.
I usually spend one weekend day a month in a massive cooking marathon. Among other items, I make a huge pot of stew. It’s about 1 lb of meat with 2 lbs of vegetables - the beauty of this is that those vegetables can be almost anything, so you can buy what’s cheap (either in season or frozen). If you then put it in the fridge overnight you can skim almost all the fat off the top the next morning, and then freeze the results. So you can get the advantage of bulk-buying some items, and the freezing keeps them from going bad. Meanwhile, when you thaw it out you can put it over noodles or rice or whatever for a reasonably balanced meal. Flavored noodle packs are cheap, especially when on sale, and can help vary the flavor.
Don’t be afraid to buy frozen vegetables - freezing actually preserves vitamins, so off-season frozen vegetables may be more healthy than their fresh counterparts that have traveled long distances.
Canned vegetables are better than no vegetables.
Buy what’s in season.
You can also make your own frozen dinners - in recent years there has been an explosion of plastic containers of all shapes and sizes. Watch for the sales. I set these up in an assebly line, About 4 ounces of lean meat (whatever sort you like) on top of rice or couscous, drizzle a little gravy or sauce on top (and since you’re doing this multiple times you can use a whole can/package of gravy without waste) with vegetables on the side. You can either buy frozen mixed vegetables (which come in different mixes, now) or individual types. Generally, the bigger the bag the better price. Put broccoli in one, peas and carrots in another, and so forth. It’s cheaper than the prepared stuff and YOU are in control of the fat/salt/other item content.
Learn to make stir-frys. Use half the meat most recipies call for and twice the vegetables. Again, you can use either in-season or frozen vegetables. Eat one serving that day and freeze the rest.
Last “cooking marathon” I did I made 8 quarts of stew and four stir-frys in about 4-5 hours. That worked out to about 32 meal-sized portions for about $40. I used ten different vegetables. I do use brown rice a lot, which does cost more than white, but is much better for you on so many levels and hey, I can afford to do so. Add in the apples and pears that are in season and that’s about two weeks of food for one, or one week for two. In reality, we eat out once or twice a week, and we do buy some convenience and snack foods so what I did last Sunday should last a month.
Back when I used to bake all my own bread I was making four loaves at a time - it takes the same amount of time, after all. And bread freezes.
Buy house brand. Shop at stores like Aldi’s - their selection varies from week to week, but their prices are low. Shop farmer’s markets and roadside stands at the end of the day or market when prices are most likely to drop or you have some bargaining power because the stand owners don’t want to haul unbought food back home.
Those with transportation problems - some chain supermarkets will take orders and deliver to those who have trouble getting to and from the store. Yes, there is a charge for this - but if your choice is a 7/11 with rotting fruit the difference in price may be very small but your choices so much greater. There are church groups and charities that may help you out - but they have to be aware you exist. Back when I was truly poor but able-bodied I traded labor (sorting, packing, carrying) for food and transportation to food for awhile. I could do this evening and weekend hours, to accomodate my need to work for money, too.
And you have to adjust your thinking - frozen orange juice, or from concentrate, is just as healthy as the “premium” never-frozen pure juice, but it’s a heck of a lot cheaper. If orange juice is high priced (which happens during a bad growing season) drink a different juice - grapefruit, for instance, or grape, or lemonade made with real lemons. You won’t die without orange juice, and there are plenty of other sources of vitamin C. Milk is expensive, yes, but if you’re cooking with milk in breads, cakes, stews, whatever you can use powdered milk for that (the off-taste is disguised in cooked foods), which can be obtained in bulk and doesn’t good bad when properly stored, and buy liquid milk solely for drinking. You don’t have to buy the high-end imported cheese - Velveeta provides calcium just like fancy cheddar does, but at a lower price.
The thing is, a lot of these techniques take time to learn or make into habits. You have to learn to be creative with what you have, rather than always seeking out specific ingredients and preparing set, unvarying recipies. You have to learn to be efficient in your time and efforts. It also helps if you have some experience cooking and are tied into folks who already know these things. If no one in your family cooks you won’t have the equipment or the know-how. If you grow up in a house where everything is deep-fried and smothered in gravy you may not be aware of alternatives.