50/50 mortgage? (shared ownership)

Hi all,

after some more advice if possible. Been talking over the possibilities og purchasing a house with my parents.

basically i'll just tell you the ideal scenario and if the people in the know could tell me if it's possible that would be fantastic.

Purchase a £100,000 house split £50,000 each, both with our own mortgages (so nota joint application but 2 £50,000 mortgages).

that way I can pay my half off over say 20 years and my parents (60 years old) can have a max 15 year mortgage for theirs - making final payment age 75 - however they would be overpaying and aiming to complete much sooner.

I would then like to purchase their 50% equity at a rate equal to a rent i.e they pay me £300 per month and I pay them £300 to buy their share on a monthly basis meaning no money changes hand and they effectively get free rent (meaning I can look after them in their retirement) and I slowly acrue 100% ownership

is this possible or would we have to have a joint mortgage?

any comments would be greatly appreciated as I would love to help them if i can and of course long term I gain a house as an investment