What is Hojokin？

What is 補助金？I am planning to buy a house through bank loan and I came to know about this word 補助金？Anyone please explain it.
Where should I apply for it? And is there any place where I can go to talk about it? It would be also great to have english website. And kind of information will help.
Thank you in advance.

"Hojokin" simply means subsidy, and there are different kinds for housing depending on what it is you are building/buying, such as subsidy for introducing home-use solar power generation system or just payment to promote housing acquisition. You'd needto ask the city hall where you are living or the bank who is offering you a bank loan.

Where did you find that information?
No contact info(TEL, URL) written in that information?

住宅補助金 are a subsidy system to support the funds of newly built houses
or renovating mainly usual, but we can not judge about you can receive or not.

Most cases are prefectures, city, town, village or other public agencies is the owner of such funds,
so you should ask at city(or ward)/town/village hall counter ASAP is the best.

This is the page about one of "Kofu City" subsidy for "house reform(renovating)"
in 2017 nendo(until H30.03) as one of sample found by looking at your profile.
https://www.city.kofu.yamanashi.jp/kenchikushido/machi/sumai/kekaku/re...
This is an explanation page of 'Housing Maker' in Yamanashi Prefecture.
http://www.j-homes.jp/subsidy/
(Even if you can read Japanese well, but it may be difficult to fully understand.)

補助金 and 助成金(josei-kin) are used interchangeably.
Some cases where only indirect subsidies such as "tax reduction" will be available even if it is either.

Maybe your bank staff knows I guess.