Tosfos Shabbos is also mesugal for parnassah. Rebbe Mordechai Lechovitzer would say, "Baalebatim complain that they don’t have enough parnassah. If they listened to me, they would keep tosfos Shabbos, and then they won’t lack anything."
Reb Mendel of Riminov zt'l said that this is alluded to in the Gemara (Shabbos 118.): עשה חול שבתך ואל תצטרך לבריות. He explained, עשה חול שבתך, bring your Shabbos into the weekdays through tosfos Shabbos, ואל תצטרך לבריות, and you will never need to ask people for financial aid.
Rebbe Noach of Lechovitz zt'l (Divrei Shmuel, Likutim 6) explained the pasuk (Bereishis 49:20) מלך מעדני יתן והוא לחמו שמנה מאשר: ר"אש are the letters before ת"שב. So אשר alludes to tosfos Shabbos, the moments before שבת. The pasuk says מאשר, from tosfos Shabbos, לחמו שמנה, one earns parnassah. והוא, from Shabbos itself, מלך מעדני יתן, one receives spirituality, ruchniyos, the King's pleasures. Because Shabbos is הברכות מקור, the root of all blessings. Shabbos itself extends spiritual blessings, and tosfos Shabbos gives us material and worldly bounty.
The Tola'as Yaakov (Sod HaShabbos 6) explains that when one keeps tosfos Shabbos, he is broadening the boundaries of kedushah, for he is turning the weekday into Shabbos. Heaven will treat him in the same way (midah kneged midah), and Hashem will expand his parnassah.
