My understanding of the way most of these equity release schemes work is that (using your example) suppose you want to release 50% of the capital – they will give you £100k (to spend as you please). However they may charge an interest rate of over 7%, which is quite high, given that it is effectively a secured loan (guaranteed on the house).
The problem is that the value of the house may not increase at the loan interest rate, resulting in the loan company getting more than 50% of the house when it is time to sell.
Let’s assume your equity release lasts for 20 years and over that time the average annual house price rise is 5%.
After 20 years, your house will be worth £531k, however the £100k loan at 7% will be £387k, so the loan company’s share of your house has increased to 73% from 50% because house price inflation did not match the loan interest rate.
If in the above example, the loan interest rate had been 8%, then the loan company’s share of your house would be 88% after 20 years - leaving very little for you.