If you said, "Busco una casa que_ tiene _tres dormitorios," absolutely everyone would understand what you meant, and no one would flinch in horror. ;-)
As English speakers, I don't think we're as forgiving of people butchering our language as speakers of other languages are of people butchering theirs (the French, perhaps, excepted). If you travel to Latin America, you'll find that most people will warm to you readily once they see that you've put in the effort to learn their language, whether you speak it well or badly! In fact, I had such a hard time getting my Ecuadorian friends to correct my Spanish, because as long as they could understand me they didn't actually think about whether what I said was "grammatically correct" or not.
That's because spoken language is not very grammatical, especially if you're talking casually among friends. If you started talking to your friends in BBC English, they'd think something was wrong with you, that you were putting on airs!
That's why I think it's much more important to focus on the "big three"-- present, preterite past, and imperfect past--rather than shortcircuiting one's brain with the conjugation of, say, "If I were rich I'd like to live in a big house."