TS Baum:
You are correct in principle, though your lomdus needs correction. The Gemora (Taanis 8b – 9a) says עשר בשביל שתתעשר, that in the nmerit of tzedokoh, one merits wealth. The Novi (Malachi 3:1) stated ובחנוני נא בזאת, from which the Chazal explained that one may “test” HKB”H with the mitzvah of tzedokoh that will merit the giver wealth. The Tur and Shulchan Aruch refer to this. Tzedokoh is the one mitzvah that one may perform without the intention of “lishmoh”, and even do so with the ulterior motive of meriting parnosoh. You are certainly on target by referencing the mitzvah of tzedokoh.