Translation:Sir, when do you want to buy the houses?
For simple yes/no questions, the normal declarative statement word order can be retained, and in writing the "¿?" symbols are used. In speaking the tone is raised at the end of the sentence.
When question words are used the Spanish question formula is:
¿(Preposition) + question word + conjugated verb + (subject) + (additional information)?
The items in parentheses are optional.