Pirkei Avot - Ethics of the Fathers

~Level 1~
Rabeinu Yonah - "whoever fulfills the torah in poverty" - he pushes off his work which he needs for his livelihood in order to fulfill torah and mitzvot. He learns torah and does mitzvot out of difficulty.

"will ultimately fulfill it in wealth" - for he will become wealthy and furthermore he will have much free time to toil in torah and fulfill mitzvot..

"whoever neglects the torah in wealth" - many times and many hours he had free time to learn but did not do so.

"will ultimately neglect it in poverty" - he will need to toil for his livelihood but will not succeed.

~Level 1~
Bartenura - "whoever fulfills the torah in poverty" - that he is pressed for his livelihood and nevertheless he annuls his work in order to toil in torah.

"whoever neglects the torah in wealth.." - due to his abundant wealth, he needs to put his mind to here and there and he has no free time to toil in torah.

~Level 2~
Ahava b'Taanugim - "whoever fulfills the torah in poverty" - some explain: one who upholds the torah and supports those who study torah while he is poor, ie with the little he has, he gives to the mouths of the torah scholars so that they can toil in torah - in the end, he will support them out of wealth. But one who annuls the torah out of wealth, ie even though he has wealth, nevertheless, he does not benefit any torah scholar and thus he causes bitul torah (annulling torah) - in the end he will anull it out of poverty. He will be dealt with measure for measure and will lose [his wealth].

Some explain: whoever fulfills the torah out of poverty of knowledge, ie even though he does not know torah, he fulfills what he heard and knows - in the end he will fulfill it out of wealth of knowledge. G-d will bestow of His wisdom to him. But whoever anulls the torah out of wealth of knowledge, ie despite his being a torah sage like Doeg, he is a wicked man and annuls the torah. In the end, he will annul it out of poverty. For he will forget his torah..

~Level 3~
Ruach Chaim - "whoever fulfills the torah in poverty.." - for the yetzer hara (evil inclination) pushes a person to not "rejoice in his portion". But if a man strengthens himself over the yetzer and learns, ultimately he will fufill it out of wealth. Namely, he will defeat the yetzer and become one who "rejoices in his portion", as Ben Azai said: "who is wealthy? He who rejoices in his portion" (Avot 4:1).

In the beginning of the diligence (b'techilat hashekeida), one has a war with the yetzer. For he longs for money, lusts, and honor, but in the end, he puts to heart to not desire in these things at all. He becomes divested of the yoke of derech eretz (earning money) and the vanities of the time and he rejoices in his portion even if it is small. For he grows spiritually (mossif shlemut). Although in the beginning he learned torah out of poverty, ie pain, afterwards he will learn torah out of wealth, namely to rejoice in his portion.

~Level 3~
Shevet Sofer, chelek 2, peticha 7 - "whoever fulfills the torah in poverty will ultimately fulfill it in wealth" - the Midrash Shmuel already asked on this mishna that our eyes see it is not so. For there are many torah scholars who study torah in poverty and did not merit wealth.

It seems to me the explanation is that in truth, man's soul longs to grand feats and to amass wealth. But one who toils in torah lishma (for its own sake) merits to realize that all is vanity. For such a person, all that his soul longs for is to increase torah. He lacks nothing and is content with the little he has. He muzzles his lusts and even if he has wealth, he does not indulge in it.. and takes only what is needed to strengthen his body for the service of G-d. Then, he comes to the level of "who is wealthy? he who rejoices in his portion" (Avot 4:1).

Thus he said: "ALL who fulfill the torah from poverty", ie even if he is still poor in his eyes, nevertheless, he is assured that through the torah, he will recognize the truth. He will come to the level of "one who rejoices in his portion.", and he will fulfill it out of wealth.

~Level 3~
Daat Sofer, Ruth - ie even though in the beginning of his torah study the poverty will be difficult on him and he will suffer in this regimen prescribed in the mishna "bread with salt, etc.", but nevertheless, if out of love, he will toil in it always (b'ahavato yishge tamid), namely, all his longing and soul's delight is solely in the torah - then "he will ultimately fulfill it in wealth". For he will be a rich man who rejoices in his portion.