In my opinion, you need to take into account following conditions.
１ The property should be located in a city that is not far from large city. But, many people are spending about one one to commute to their office. So, you do not need to find property that is very close to center of Tokyo.
In Japan, if you take a train you can go to Shinjuku station from Omiya station within 40 minutes by train ( train fee is 470 yen. ).
Omiya station is located in Saitama prefecture.
When foreign national try to find investment property, many of them try to find in very urban area like Minato ward, Shibuya ward, Shinjuku ward.
And they will notice that they can not purchase it with their budget.
Moreover, in this area, yield on investment is very low.
And the amount of property tax is very high. It will surely reduce your profit.
If a property is located in rural area, but it is close to large firm, factory, office, you can have a chance to get high yield profit.
When there is a large firm, many people are working there and some of them want to live close to their office.
Even if the office is located in rural area, if you purchase investment property near the office, worker will rent your apartment.
And if a property is located in rural area, you can purchase it at low price and can expect high yield rate.
So, you need to look for an investment property at broad area.
２ The property should be located at within 20 minutes from the nearest station.
Some of potential investors look for property that is located at within 10 minutes from the nearest station.
But there are many competitors to purchase such property and you do not have any chance to purchase it at reasonable price.
Even if a property is located at 20 walk distance, renter can use bicycle and go to station within 5 minutes.
And in the case of detached house, distance from station is less important than in the case of apartment.
Because, renter can use car to go to their offices. ( Of course, existence of parking space is important. )
３ Even if there is not a renter, it is not a problem. Because, if there is already a renter, it is difficult to demand discount of selling price. If there is not a renter and current owner is suffering from it, possibility of discount of selling price will increase. Current owner wants to be relieved of his anxiety.
You may want to purchase an investment property that has already renter. Because, you do not want to be worried about finding a renter.
But, if there is a sound renter and owner can receive money from renter, why is he going to sell the property at low price ?
Of course, you need to examine whether you can find your renter or not.
And you need to know the reason why seller could not find renter.
Was he just a lazy person and did not anything to find renter ?
Did not have budget to repair the room to attract renter ?
Or are there too many investment properties in the area ?
4 Even if a property is old, it is OK as far as the property is duly maintained.
Or even if condition is bad, as far as the selling price is cheap, it is OK.
If a selling price is cheap, there should be some problems. And as far as you （ with my help ） can solve the problem, it may be nice property to purchase.
５ You need to find a person who can assist you to find a suitable property in Japan. Many of foreigners who live outside of Japan try to find nice property on the internet.
But, in the case of experienced investors.
In the case a realtor ( Hereinafter referred to Yamada realtor )gets order from a owner to find buyer, if a property is nice, they do not want to display it on the internet ( Every realtor can share this information, ordinary people can not access this information. Called REINZU).
If the realtor can find a buyer by himself, he can receive fee from seller and buyer. But, if the realtor share the information of the property on REINZU, other realtor may find buyer.
In that case, Yamada realtor can receive fee from only seller. So, if a property is nice, they do not display the prperty on the internet.
In order to get information of such property, you need to contact with local realtor in person.
And if you order me, I can move around to get such kind of information.
And if I find suitable find, you need to apply to purchase it at once. They can not wait for your decision for several day