Remodel your double wide and add a sun room. The expense of this endeavour will vary and may have to be done by a professional. As it's very unusual to see a double-wide mobile home that has a sun room, this will certainly make your double wide appear more like a house.
Add vinyl exterior shutters to the windows of your double wide. Shutters are usually found on windows of older style homes and they are unusual on mobile homes. They not only add style to your double wide, but they will make it look more like a house. Exterior shutters come in a multitude of colours and styles, depending on your preferences.