If a doctor is called to treat an ill patient on Shabbat, he is allowed after Shabbat to charge for his services. Generally speaking, it is forbidden to accept payment for work done on Shabbat. However, Halacha makes exceptions in this regard for services involving a Misva, such as in the cases of Hazanim and Rabbis who work only on Shabbat. This exception applies to medical services, as well, and thus a doctor may charge for treating a patient on Shabbat. This is the ruling of the Shiyureh Kenesset Ha’gedola and other authorities, as cited by Rabbi Moshe Halevi (Israel, 1961-2001) in his work Menuhat Ahaba (vol. 1, chapter 10; listen to audio recording for precise citation).
Is it permissible to rent a hotel room for only Shabbat?
When a person rents a hotel room for a several-day period which includes Shabbat, then this is clearly permissible because he pays one lump sum for the entire period, and he does not pay separately for Shabbat. This is akin to a person hired to perform a certain job all week, including Shabbat, who may certainly receive the full salary, because his payment for Shabbat is incorporated into the total sum, and he does not receive a separate payment for working on Shabbat. But may a person rent a hotel room only for Shabbat, given that he is paying specifically for services rendered on Shabbat?
The Menuhat Ahaba cites the Sitz Eliezer (Rav Eliezer Waldenberg, Jerusalem, 1915-2006) who rules (in vol. 7, Siman 28) that it is permissible to rent a hotel room for only Shabbat. The money paid to a hotel is for not only the use of the room, but also for the food which is offered to him as part of the arrangement. We may therefore consider the payment for use of the room as incorporated within the overall payment, which includes other services, such that no payment is made specifically for services rendered on Shabbat. (Of course, this assumes that food is indeed offered as part of the rental agreement.)
Summary: A doctor who is called to treat a patient on Shabbat may charge for his services after Shabbat. It is permissible to rent a hotel room for only Shabbat, and it goes without saying that one may rent a hotel room for a several-day period that includes Shabbat.