each month, in each month

I believe you typed in the second "money" by mistake, and you meant it to be "month".

So the two sentences in your question should have been:

he would receive $40 of money each month.

he would receive $40 of money in each month.

Both sentences contain error, but seem to carry the same meaning.

I think the correct sentence should be:

he would receive $40 in cash each month.

reason:
(1) if the word "money" here represents the actual bank note, then the words "in cash" should be used when the dollar amounts are stated.
(2) it is either "in each of the months" or "each month". Since the time period is not specified, it is better to use "each month".

Based on the two sentences presented in your question, I could not see how they had meant to convey a different meaning. They both mean, as explicitly stated, that he would receive $40 dollars a month, and if the word "money" means cash, then the words "in cash" will identify that.

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