This summer, master the Yiddish language with Yiddish In 10 Lessons
one that invites trouble upon himself
על מי שנכנס מרצונו לעניין שגורם לו צרות אומרים
זיך אײַנקויפן אַ מפטיר
zikh aynkoyfn a mafter
to buy yourself a *maftir
קונה לעצמו מפטיר
*Maftir properly refers to the last person called to the Torah on and holiday mornings: this person also reads the haftara portion from a related section of the Nevi'im (prophetic books).
Informally the portion of the Torah read by or to the maftir is called the "maftir portion", or the "maftir" for short. On a normal Shabbat morning seven people are formally called up to the Torah, and a part of the week's Torah portion is read by or to each of them. The maftir is not counted among the seven, and is not formally called up by name: on the conclusion of the seventh reading the reader simply calls "maftir" and repeats the last few verses to the maftir. Many shuls have the custom on Shabbos and Holidays to auction off the honor of being called to read the portion of the Torah. Maftir is one of the paticularly desirable portions and usually sells well. Hence the expression above.
Yiddish is rich with expressions. In fact, sometimes the same phrase can be said in a number of different ways. I try to bring the unique ones, where it is is not obvious from the literal translation what the expression means.