Depends what you mean by poor and healthy. If you are really struggling your local market at the end of the day is good because they will often throw out quite edible vegetables and fruit that though bruised or damaged can be cut around and used. Ask and they may let you have it for free or a greatly reduced price. If you really want to eat healthy try and avoid too much pasta,potatoes and rice (unless it's brown rice) and keep your protein content up because it will not mess with your insulin levels like too many simple carbs will, and will actually leave you feeling full without ruining your waistline. Not just meat, beans, nuts and legumes. You can eat a lot of complex carbs in vegetable form, something like Green Beans

We have never had much money but always manage to eat well.