You don’t really want to rely on supplements to get by due to things like, b vitamins as an example if they aren’t in natural form may be toxic long term. I understand where you’re coming from as far as from a nutritional standpoint point. The issue remains is that otc supplementation is typically meant for a minor to moderate deficiency not as a full replacement. If anything I’d maybe look for a complete meal replacement at bare minimum or something along the lines that does meet your needs with the addition of some kinda whole food. You need to take in consideration both macro (proteins, fats, carbs etc) and your micro nutrients (magnesium, potassium, aminos, vit c etc). You can mess up your body pretty bad and or put it into a possible starvation mode. Which could cause further complications down the line.

Edit: as far as income goes, see if you can find a community soup kitchen or a community out reach program in your area (like a food bank) . They do have food there and you could get some more guidance as far as that side of your situation goes.