We took one out 5 years ago to pay for an extension to our then home. We approached the Nationwide, both our banker, and we had previously had a mortgage with them. The amount we were borrowing was less than 10% of the value of the house and the payments were, for us, easily manageable. We have just sold the house and have repaid RIO.
There are 2 considerations when thinking about a RIO mortgage, firstly, how long you want it for. We took ours out knowing we would probably be downsizing within 5 years and the extension, apart from improving our house and making it more enjoyable for us to live in would significntly increase the houses value and saleability.
How long you want the mortgage for leads to the second key consideration. Can you comfortably afford the monthly interest payment, not just now but in the future. We knew that our RIO mortgage would only be for 5 or 6 years so knew we could manage the interst payments easily
But we are the generation that remembers 10% plus mortgage interest rates. I do not know how old you are but if you are in your 60s and wanted a long term mortgage you could be paying interest for 20 plus years or more. Could you manage the interest rates if they doubled - or trebled?
I think that, with caution a RIO can be very useful if you want to extend a house or adapt it for old age living, but if it is to improve your standard of living I would be less sure. In that case you would be better with equity release.
I say that because with equity release, you do not have to role up the interest. You can pay the interest rate monthly as with an RIO so that it acts like an RIO, but you have the flexibility that if something changes, or, long term, interest rates escalate, you can later decide to role up some or all of the interest rates.