If it is a high end housing product you may have to use a designer because they have access to some material/finish suppliers that are otherwise unavailable but that tends to only be for the highest end housing deliveries.

Sorry for the slow response had a wedding to prepare for at my house and just in recovery after being in the hospital.

Many successful investors started small, such as with house hacking or buying affordable properties to rent out.

No loan, I paid cash for the 5 acres and built a pole house myself. 

This is more of a reach goal for me since I am still in my "collect 4 green houses before trading up to a red hotel" stage, but I thought I would ask the hive mind anyways.

If she went to buy a house and applied for a mortgage, I think the lender would say the same thing aka you don't qualify until you get this removed from the credit report.

If it does go to probate, hopefully your brothers and you can amicably go the informal route vs formal (I've worked with families in both when buying properties out of probate and informal is FAR easier).Since there's no debt on the house, maybe you could sell with financing or maybe you could even buy out your brothers with financing -- that way you maintain ownership and just pay them a monthly amount.

Your time is worth money, it's time that guests aren't renting your house. 

Mike Lambert above is correct about house values in Japan.

If I were in your and/or your mother-in-laws shoes, I would go to a local bank and use the free and clear house to secure a $150K+ line of credit.