In a separate bowl, combine yeast and 4 cups flour; mix thoroughly. Add flour mixture to butter/sugar mixture, then add the hot water. Mix well and add an additional 3-1/2 to 4 cups of flour, 1 cup at a time, until soft smooth dough forms. Turn out on lightly floured surface and knead until smooth. Place dough in a greased bowl, cover and let rise until double in bulk, about 45 to 50 minutes.
Divide dough into 3 equal portions. For each portion: roll out to an 8x14-inch rectangle. Brush with 3 tablespoons melted butter. Combine 1 cup sugar with cinnamon to make cinnamon sugar. Sprinkle 1/3 cup cinnamon sugar and 2/3 cup pecans on each rectangle. Roll up from short side. Cut each roll into 8 slices.
For Caramel Syrup:
Melt butter in a saucepan. Add brown sugar, corn syrup and vanilla. Stir until blended.
Place 1 cup caramel syrup and 1 cup pecans in each of three 13x9-inch pans. (or 1/2 cup syrup and 1/2 cup pecans in 8-inch square baking pans). Place 8 rolls per 13x9-inch pan, or 4 rolls per 8-inch pan, cut side down. Cover and let rise until double, about 45 to 50 minutes.
Bake at 325ºF for 15 to 20 minutes for 8-inch pans and 20 to 25 minutes for 13x9-inch pans. Cool slightly before turning out of pan.