Private mortgage

Deniseconfused

I want to lend someone ( my partner ) around £50,000 secured on his mortgage free house ( value £500k)  No interest charged and only payable from his estate when he dies. I have several properties myself and we dont live together as I like my own space, and I dont want to pay the additional stamp duty to "buy in" a share of his house or want the hassle to do so. A private mortgage seems the simplest answer. I want it worded that instead of interest, I just get 10% of the sale proceeds - so I benefit from any increase. 

Are these still a thing nowdays etc ? 

Cheers x 

DullGreyGuy

So you mean £50k on death or sale, whichever the sooner plus 10% on the sale whenever that may be?

What if they sell the property to their kid for £1? £50,000.10 payable?