Is it permissible to buy a house with a 5% interest rate in America, and is there a specific limit for the permissible interest rate?

If the intention is for the husband to take an interest-based loan from the bank to buy the house, then this is forbidden and is one of the gravest sins, whether the increase is small or large, and calling it "interest" does not change its ruling. However, if the intention is that the homeowner increased the price because the sale is deferred over installments, then this is permissible if the price and its deferment are agreed upon.