Never buy a painting made of house paint. As sure as house-painted walls become grimy and need to be repainted with fresh coats, so will that painting you bought and that you thought was a good bargain.

Using house paint is fine when an art student cannot afford materials and is mastering technique in tone and in color-mixing, but the end products should not be passed off or sold as professional-grade works.

If, however, you fell in love with that house-paint painting and would like to keep it a long time, have it varnished immediately--and keep it away from direct sunlight (yes, it will fade).