An alert chimed on John's phone and he quickly glanced down. The message was enough for John to quickly change his focus, and now he was eager to leave. He raised his hand to get the waitress' attention, and told Sherlock, "Out of all of them? I liked the brownstone, too," he admitted. I just... I guess I just was worried that it might be too much. It's not so much an apartment, it's more like a compact house."
John's unconscious anxiety came from the idea that a house meant something more significant than an apartment. It meant domesticity. It suggested family. And while he was headed in that direction with Sherlock, Harry and now a puppy, it still worried John on a certain level. Mainly, what sort of husband would he be to Sherlock? Would he be as awful as his father to his mother? Would he be a lousy father?