If possible, take photographs of each house: the outside, the major rooms, the yard, and extra features that you like or ones you see as potential problems. And don't hesitate to return for a second look.
Use the right solvent to clean up paint equipment. Check the paint can label. Generally use a mild detergent solution for water-based paints, mineral spirits for alkyd enamels, mineral spirits or turpentine for oil paints, alcohol for shellac, and mineral spirits for varnish. When you are reusing solvent for cleaning equipment, occasionally rub some between your fingers. When it begins to feel sticky, dispose of properly.