וְלֹא שֵׁבֶט לֵוִי בִּלְבָד, אֵלָא כָּל אִישׁ וְאִישׁ מִכָּל בָּאֵי הָעוֹלָם אֲשֶׁר נָדְבָה רוּחוֹ אוֹתוֹ וֶהֱבִינוֹ מַדָּעוֹ לְהִבָּדֵל לַעֲמֹד לִפְנֵי ה' לְשָׁרְתוֹ וּלְעָבְדוֹ לְדֵעָה אֶת ה', וְהָלַךְ יָשָׁר כְּמוֹ שֶׁעָשָׂהוּ הָאֱלֹהִים, וּפָרַק מֵעַל צַוָּארוֹ עֹל הַחֶשְׁבּוֹנוֹת הָרַבִּים אֲשֶׁר בִּקְּשׁוּ בְּנֵי הָאָדָם --הֲרֵי זֶה נִתְקַדַּשׁ קֹדֶשׁ קֳדָשִׁים, וְיִהְיֶה ה' חֶלְקוֹ וְנַחֲלָתוֹ לְעוֹלָם וּלְעוֹלְמֵי עוֹלָמִים; וְיִזְכֶּה לוֹ בָּעוֹלָם הַזֶּה דָּבָר הַמַּסְפִּיק לוֹ, כְּמוֹ שֶׁזִּכָּה לַכּוֹהֲנִים וְלַלְּוִיִּים. הֲרֵי דָּוִיד אוֹמֵר "ה', מְנָת-חֶלְקִי וְכוֹסִי--אַתָּה, תּוֹמִיךְ גּוֹרָלִי" (תהילים טז,ה).
Not only the tribe of Levi, but any one of the inhabitants of the world whose spirit generously motivates him and he understands with his wisdom to set himself aside and stand before God to serve Him and minister to Him and to know God, proceeding justly as God made him, removing from his neck the yoke of the many reckonings which people seek, he is sanctified as holy of holies.
God will be His portion and heritage forever and will provide what is sufficient for him in this world like He provides for the priests and the Levites. And thus David declared [Psalms 16:5]: "God is the lot of my portion; You are my cup, You support my lot."
Blessed be the Merciful One who provides assistance.
This text of Rambam is praised by commentaries as worthy of his author.
Rambam paraphrase of a verse in Kohelet 7, 29:
לְבַד֙ רְאֵה-זֶ֣ה מָצָ֔אתִי אֲשֶׁ֨ר עָשָׂ֧ה הָאֱלֹהִ֛ים אֶת-הָאָדָ֖ם יָשָׁ֑ר וְהֵ֥מָּה בִקְשׁ֖וּ חִשְּׁבֹנ֥וֹת רַבִּֽים:
Behold, this only have I found, that God made man upright; but they have sought out many inventions {literaly counts}.
Following the Midrash Kohelet this verse is a reference of humanity before the sin:
יָשָׁר הָיָה, שֶׁנֶּאֱמַר: אֲשֶׁר עָשָׂה הָאֱלֹהִים אֶת הָאָדָם יָשָׁר, וּכְתִיב (בראשית ג, כב): הֵן הָאָדָם הָיָה כְּאַחַד מִמֶּנּוּ, כְּאֶחָד מִמַּלְאֲכֵי הַשָּׁרֵת, וְכֵיוָן שֶׁנַּעֲשׂוּ שְׁנַיִם, וְהֵמָּה בִקְשׁוּ חִשְׁבֹנוֹת רַבִּים.
He was upright, as is stated in Genesis (3, 22): " the man has become like one of us,". Before the sin, humanity was not mislead by livelihood.
Apparently the Rambam refers to two Chazal statements: the first is a Mishna in Masechet Avot:
כָּל הַמְקַבֵּל עָלָיו עֹל תּוֹרָה , מַעֲבִירִין מִמֶּנּוּ עֹל מַלְכוּת וְעֹל דֶּרֶךְ אֶרֶץ.
One who accepts upon himself the yoke of Torah is exempted from the yoke of government duties and the yoke of worldly carrier
and the second is a Gemara that we can found in several places with little changes in version, here BK 38a:
התניא, ר"מ אומר: מנין שאפילו נכרי ועוסק בתורה שהוא ככהן גדול?
ת"ל: (ויקרא י"ח) אשר יעשה אותם האדם וחי בהם, כהנים ולוים וישראלים לא נאמר אלא אדם, הא למדת, שאפילו נכרי ועוסק בתורה הרי הוא ככהן גדול
Rabbi Meir used to say, Whence can we learn that even where a gentile occupies himself with the study of the Torah he equals [in status] the High Priest? We find it stated: Which if a man do he shal live in them;(17) it does not say "priests, Levites and Israelites", but "a man", which shows that even if a Gentile occupies himself with the study of the Torah he equals [in status] the High Priest.'
Humanity is facing by a great complexity of issues. That is a consequence of loving complications. This complexity of life is the state of the world after the sin (אחרי החטא). Some exceptional individuals, driven by their deep desire, spend spontaneously their live to the cause of causes. In such a case, he is blessed: "וחי בהם", "ה' מנת חלקי וכוסי אתה תומך גורלי". Concerning the Tribe Levi, Mitsvot have resulted from this.
We see a Blessing a Promise, a guaranty, not from social organization (not Tzedaqa or Collel, Isachar-Zvulun), not a Social Status. The tribe of Levi is only an example of destiny. But concerning the tribe of Levi, some Mitzvot are an "institutionalization" of their blessing (Maaser Rishon).
From Hilchot Talmud Torah Rambam we understand that he need to work to avoid alms. And in Hilchot Sheviit, Rambam garantees blessing to a man who doesn't at all abandon all work, as Shevet Levi, But doesn't devote himself to the pursuit of money.
This man, on Hilchot Sheviit earns little money but it's enough for himself, he is not afraid to live in poverty, not as a man which received a lot from community. As a Levi who is not afraid that he earns less money than a landowner
The special blessing is for Tzadikim. Every individual on its own merits will found a work that allow to learn Torah and perform Avodat Hashem. Rambam states explicitly that the Hashgacha is proportionally to the degree of proximity of the Tzadik.
Note: The famous Machloket between Rambam (lengthly developed in Avot 4) and most comments about the legitimacy of make money with Torah learning, Torah crown is not our topic.
