How to express gratitude as a house guest?
an approach that's formal, more "literary chinese":

對府上之款待﹒先行拜謝

"先行拜謝" is, roughly "thank you in advance"

"府上" is the honourable term of "your home", you may change it to "貴府", "貴寓", or "尊府

http://dict.revised.moe.edu.tw/cgi-bin/cbdic/gsweb.cgi?o=dcbdic&amp;searchid=Z00000038602

"款待" is, roughly "reception"

http://dict.revised.moe.edu.tw/cgi-bin/cbdic/gsweb.cgi?o=dcbdic&amp;searchid=Z00000078380