You need to write "who" after "a few people" (remember Verb Agreement) in the sentence, otherwise it would be incorrect. "Housing prices have skyrocketed in this decade. That is why there are only a few people who can afford to buy houses." Everything else seems fine, as per my knowledge. Also, is this part of any formal draft? Here's an alternate: "In this decade, the housing prices have skyrocketed. Consequently, a few people can afford to make a purchase".