"Ver casas en venta" in Spanish means "to see houses for sale" in English. According to SpanishCentral.com, "ver" means "to see." However, "ver" is a verb in Spanish that also can mean "to look at." Thus, the phrase could also be translated as "to look at houses for sale."
When one sees the phrase "ver casas en venta," most likely the person using the phrase is looking for, or is wanting to see, houses that are for sale. It is possible that the person using the phrase in Spanish is perusing the Internet or elsewhere seeking houses being sold on the real estate market.