If you are looking for a mayo substitute just mix some greek yogurt with a little lemon juice, a little sugar or agave syrup, a little salt, a tiny amount of spicy mustard and a little cider/wine vinegar. Tastes near the same and give you a similar consistency.
I have relatives who use Hunt's or Del Monte Ketchup. If that's the kind of garbage you are used to eating at home I can see how you might be tempted to make your own ketchup. In 1994 Malcolm Gladwell wrote in this essay that Heinz had perfected and patented the perfect blend of ketchup ingredients. There is no reason…