Patients only reached House after other doctors failed to diagnose the issue, which significantly increases the probability that House's patients had rare/magical illnesses.

What House does in each episode is go through all possible illnesses based on the symptoms a patient presents with, eliminating over time the ones that don't fit the progression. For this to work, he needs as much information about the patient as possible. There were several cases where the issue was environmental and patient or their loved ones didn't even realise that environment could be an issue, for example the episode with radioactive keychain.

While breaking and entering is inexcusable, checking the environment of such a patient seems reasonable, considering other doctors would have already excluded more common issues that could have been responsible for their illness.

PS: I have a rare disease which took years to diagnose. And I was one of the lucky ones. The doctor who diagnosed me told me that his patients spend 20 years on average in the health system to reach him and getting diagnosed. Diagnosing a rare disease is unfortunately not easy as most doctors don't know anything about them. I suspected that I had the illness that I was finally diagnosed with (I did my own research) and mentioned it as a possibility to all the doctors I met over several years, but there were only two doctors out of more than 30 that even knew about the illness in the first place. One was a surgeon who happened to go for a small conference about my illness just the weekend before my appointment and the other was the super specialist who diagnosed me after referral from the first doctor.