Tourist buying a mansion (condo) in Japan

We are a retired couple in our 50's, living in Canada. We love Japan and have been going there 8-9 times a year, 1 week in duration each time, as tourists when we were working.
We are planning to buy a condo unit in Japan. We plan to stay there 5 months in a year in the winter and stay in Canada for the rest of the year. While in Japan, we will visit other Asian countries too but we would like a base in Japan because Japan offers the best food!
Now comes the problem. As temporary visitors, we cannot get a Zairyu card and hence cannot get a bank account. How do we pay for the expenses of the condo, especially when we are absent 7 months in  a year?
I can think of one way, to become an (old) student and get a student visa. Then open an account. But this is not a preferred way as we don't want to tie ourselves down to go to school . Also,  would the bank close my account once my visa expires?
Any other idea is welcome. Thanks in advance for all your help.

hire someone. generally speaking, a real estate, at which you buy your property, may take care of such things, or recommend you another person.

when you get a student status, and not go to school, it is illegal. in the worst case, you may be refused to enter Japan.

This page explains how to buy real estate from abroad.
https://fudousan-kyokasho.com/foreign-real-estate-purchase-738

Without resident card in Japan, you can purchase a real estate and register it by your name.

As far as you can find suitable real estate in Japan, you can hire a lawyer (scrivener).

He will contact local real estate company and act as your agent.

He will prepare necessary documents and file ownership transfer registration from seller to you.

You can complete this transaction without your bank account in Japan.

Sorry for being direct, but if you cannot contact the right organization in Japan for foreign investment or get the required information, how will you manage your investment?

Japan has rules (specific) like any other country.
You need to find a real estate who is specialized in supporting you and who can give you customized advise based on your situation.

We plan to stay there 5 months in a year in the winter and stay in Canada for the rest of the year. Your visitor permit will allow a 90-day stay. Staying 5-months is possible with a special visa, but that requires a different application.
While in Japan, we will visit other Asian countries That helps to get around the 90-day problem above.
How do we pay for the expenses of the condo Pay from your accounts in Canada - lots of international transfers or link to a credit card. Quite do-able if your building association allows for that.
I can think of one way, to become an (old) student and get a student visa. Then open an account. But this is not a preferred way as we don't want to tie ourselves down to go to school . Also, would the bank close my account once my visa expires?
Don't. Immigration is requiring (or at least planning to require) that schools measure attendance and students actually go to school. If you don't that could damage your ability to visit. And, yes, the bank will helpfully suspend/cancel your account on your visa expiry.

Schools are already registering attendance and reporting it. Not a terribly new requirement.

To your other question, if your account will be closed once you stop residing in Japan, well, actually no. I left Japan 2 years ago (but still come here frequently for business) and just reported to my bank my new address back in EU, and they were quite happy with that. I maintain my Japanese bank account and my Japanese credit cards. I know it sounds strange, because of how difficult it is to get a credit card in the first place, but once you are a customer they are happy to keep you.

So IF you are willing to really become a student for some time, the student visa very well might be an option. This would require that you really attend school, but then you want to live in Japan, so learning some Japanese would definitely be good. So maybe you should plan to do at least 6 months, maybe longer of Japanese studies in a Japanese language school, do that on a student visa, get settled and once that is done, you can start travelling through Asia and going back to Canada on regular basis.

Note, that travelling outside of Japan while at school often requires a permit from the school and you wont be allowed to do it during class time. (I mean ultimately the school can't force you to stay, but they can make problems with your visa if your attendance is low). Student visas are meant for people who actually do study, so it makes sense that attendance is a factor in guaranteeing the visa.

@Likebike - I should clarify on the bank account issue. I have two main accounts, one personal, one business. For my business account my bank kindly/bluntly informs me each year that they will cancel or suspend it at the expiry of my visa. So each year I post a photocopy of my resident card to an office in Fukuoka (an email scan is not sufficient, they require a piece of paper). It depends on the bank.
For my personal account, that bank is a bit slack in some of their procedures (and annoying in others). I recently got a letter asking for some proof about the MyNumber system as it is an annual requirement they have - first time in three years.