The Rebbe's guidance on tzedakah and maaser in connection with livelihood:
Tzedakah is both the source and the vessel of parnassah. "Aser bishvil shetisasher": giving brings blessing, as Hashem promised (IK 493, 3205, 3584). Make Hashem a partner in the business through tzedakah and honest dealing, and the blessing goes beyond natural limits (IK 2856, 5833). Care in giving tzedakah is directly connected to one's livelihood (IK 2496).
When starting a business, commit a portion of its profits to tzedakah from the outset (IK 1637, 5915).
In hard times, don't cut back on tzedakah. Financial difficulty is a test; maintain or even increase the giving rather than reducing it (IK 2194, 6248). Give frequently, especially daily before davening (IK 5686, 9118). Where it is truly impossible, give half the maaser now and record the other half as a debt to be paid when able (IK 6413). Keep up maaser even in uncertain times (IK 6873). Material difficulties can be connected to not having given maaser properly, and correcting this brings blessing (IK 5879).
Wealth is a trust. Hashem entrusts money to a person as a test and a mission, to be used for tzedakah as intended (IK 1884). As earnings grow, the giving should grow with them (IK 7086), and financial gains should serve as vessels for spiritual growth (IK 6581). Extra tzedakah is best spread across several recipients or causes (IK 3139), and maaser given to Torah education brings special blessing (IK 5128).
See also: עשר בשביל שתתעשר; פרנסה – ביטחון ודאגה.