Что касается имущественного вычета, то он зависит от процентов по ипотеке.

Что касается ... is a set expression meaning as for ..., regarding ..., or when it comes to ....

So:

• Что касается имущественного вычета, ... = As for the property deduction, ...

This structure is often used to introduce a topic and then comment on it. It is quite common in both speech and writing, and it sounds a bit more formal or organized than a very casual phrasing.

A very common pattern is:

• Что касается X, то Y. = As for X, Y.

Because что касается requires the genitive case.

The dictionary form is:

• имущественный вычет = property deduction

But after касаться / что касается, it changes to genitive:

• имущественного вычета

So this is not because the meaning changes; it is simply the case required by the expression.

Compare:

• Это имущественный вычет.
  Here it is nominative.
• Что касается имущественного вычета, ...
  Here it is genitive.

In Что касается X, то Y, the word то helps mark the second part of the sentence: the comment about the topic just introduced.

So:

• Что касается имущественного вычета, то он зависит ...

You can think of it as a discourse marker linking the two parts:

• As for the property deduction, it ...

In English we usually do not translate то separately. It often has no direct word-for-word equivalent here.

It is very common in this pattern, but in some contexts it can be omitted:

• Что касается имущественного вычета, он зависит ...

That is still understandable, though то makes the structure sound more complete and natural.

Он refers to имущественный вычет.

Why он?

• вычет is a masculine noun
• so the pronoun used for it is он

Even though the full phrase is имущественный вычет, the head noun is вычет, so the pronoun matches that noun.

Yes. Russian uses the verb зависеть with the preposition от, and от takes the genitive case.

So:

• зависеть от чего? = to depend on what?

Literally, English speakers may feel it is closer to depend from, but the natural English translation is still depend on.

In this sentence:

• он зависит от процентов ... = it depends on the interest ...

This is just a normal Russian pattern you need to memorize:

• зависеть от + genitive

Here процентов is the genitive plural form of проценты.

Important point: проценты can mean either:

• percentages
• or interest (for example, bank or loan interest)

In this sentence, because of ипотека, it means interest:

• проценты по ипотеке = mortgage interest

And because the phrase follows от, it becomes genitive:

• от процентов по ипотеке

So:

• nominative: проценты по ипотеке
• genitive after от: процентов по ипотеке

По ипотеке means on the mortgage or related to the mortgage.

The noun is:

• ипотека = mortgage

After the preposition по, it is in the dative case:

• по ипотеке

This is a common Russian pattern in financial contexts:

• проценты по кредиту = interest on the loan
• выплаты по ипотеке = mortgage payments
• долг по кредиту = debt on the loan

So по ипотеке is not random; it is the standard way Russian expresses this relationship.

It is something fairly specific.

• вычет = deduction
• имущественный = property-related

In Russian legal/tax language, имущественный вычет usually refers to a property tax deduction, often connected with buying real estate and sometimes also with mortgage interest.

So even though the words literally look like property deduction, in practice it usually refers to a specific tax concept, not just any deduction involving property.

Yes, but the original order is very natural because it presents the topic first.

Original:

• Что касается имущественного вычета, то он зависит от процентов по ипотеке.

This works like:

1. topic: as for the property deduction
2. comment: it depends on mortgage interest

You could rearrange things, but the sentence may sound less neutral or less smooth. For example:

• Имущественный вычет зависит от процентов по ипотеке.
  This is simpler and more direct.
• Что касается имущественного вычета, он зависит от процентов по ипотеке.
  Also possible, just without то.

So the original version is especially good when the speaker is switching to that topic or contrasting it with something else.

Yes. A few common alternatives are:

• Насчёт имущественного вычета, ... = about / as for the property deduction
  More conversational.
• Относительно имущественного вычета, ... = regarding the property deduction
  More formal.
• По поводу имущественного вычета, ... = concerning the property deduction
  Neutral and common.

But Что касается X, то Y is a very standard and useful structure, especially in explanatory or formal speech.

Here are the main forms:

• что = what
• касаться = to concern, to relate to
• имущественный = property-related
• вычет = deduction
• то = that / then / a linking particle, depending on context
• он = he / it
• зависеть = to depend
• от = from
• проценты = percentages / interest
• по = on / according to / related to
• ипотека = mortgage

And here are the forms actually used in the sentence:

• касается = 3rd person singular present
• имущественного = genitive singular masculine/neuter adjective
• вычета = genitive singular
• зависит = 3rd person singular present
• процентов = genitive plural
• ипотеке = dative singular

The main stresses are:

• что каса́ется
• имýщественного or more commonly имýщественный in dictionary form
• вы́чета
• зави́сит
• проце́нтов
• по ипоте́ке

A learner may especially want to remember:

• зави́сеть
• проце́нт
• ипоте́ка

Stress is important in Russian, so it is worth learning these together with the words.

Yes—three very useful patterns:

1. Что касается + genitive

   • Что касается этого вопроса, ...
   • Что касается цены, ...

2. зависеть от + genitive

   • Это зависит от времени.
   • Всё зависит от ситуации.

3. проценты по + dative in finance

   • проценты по кредиту
   • проценты по займу
   • проценты по ипотеке

If you remember those three chunks, the whole sentence becomes much easier to understand and reuse.