I would like to know how to say that correctly and whether some/any could stand as a subject in the sentence:
Could you lend me ... money? Sure, If I find some/any.
The most natural way to ask this question is "Could you lend me some money?" You aren't asking a question, you are making a request, therefore some is the word to be used. Similarly, when you offer someone something, you don't use any but some, for example: "Would you like some money?" In both cases you sort of expect the answer to be positive.
As for the answer to this question, both "If I find some" and "If I find any" are correct, but in the latter you indicate that the possibilities to find the money aren't many.
You could use some or any in the leading question, but I would favor some instead of any in the response:
Why? Both words are relatively close in meaning, and both can be used as adjectives or pronouns (which is how they are being used in the first and second sentences, respectively). But look at the nuances in meaning:
In the answer, you are essentially saying, "Sure, I would lend you some money, if I had an unspecified amount of money."