It is a Mitzvah and obligation to host paupers, orphans, widows and other unfortunate individual’s as guests for one’s Yom Tov meals. One who refuses to do so, is not considered to be having a meal of a Mitzvah, but rather a one of abomination.
It is forbidden to invite gentile guests on Yom Tov, for the Yom Tov meal. If, however, the gentile arrived on his own, one may offer him and give him to eat, although it is forbidden to press on the gentile to eat if he does not accept the initial offer.
Housemaid: It is permitted to have a gentile housemaid eat the Yom Tov meals with one’s family.
 Admur 529:11 “When one eats and drinks on Yom Tov he is obligated to feed converts, orphans and widows, amongst all other unfortunate paupers. One who locks the doors of his home and eats and drinks with his wife and kids alone and does not feed or give to drink the paupers and people of misfortune, their meal is not considered a Simchas Mitzvah, but rather a Simcha of their stomachs. On this the verse states that their bread is impure, and it is as if they have placed manure on their face. This form of joy is considered a mockery of themselves.”; Rama 529:1; Rambam Yom Tov 6:18
 Admur 512:1; 325:1
 The reason: It is forbidden to invite gentile guests on Yom Tov due to a decree that one may come to cook more food on his behalf. [ibid]
 Admur 512:2
 Admur 512:3