The percentage doesn't matter a great deal. It has everything to do with serviceability of the debt.
If homes were $150,000 for 3bed 2 bath. 20% interest rate on mortgage would be $3000/monthly or $36,000/year amortized for 10 years.
Kind of crazy but doable. The key point is the $150k and not $1mil. So as interest rates go up, the affordability of the homes goes down and so they cant sell for the same $.
The average rent price will also be really similar to whatever this service rate is. So if the best mortgage rates are coming in around $3000/month. Rent will be that much more or less. The key ROI or rent vs buy is that you are paying into equity when buying. So you'll find rent vs buy is usually measured in months. That is to say, if you're staying in the general area of the city or whatever. You might as well buy so long as you'll stay for about a year.
Though this is a risk. If housing crashes in price because of brain drain exodus out of a region, or immigration were to be shut down, or politicians in general being bad causing the crash. Then you might end up owing more than its worth. However, it's an important detail, much of a country's wealth is in its developed land. So when housing crashes, it's literally dropping the wealth of the country. That's a sure way to get your head chopped off as a politician.