What is fair - Deed of Trust

[TheEmmaDilemma]

I would like some opinions on what is fair to put in a deed of trust.

My Partner and I intend to move from my Interest Only mortgage to a joint Repayment mortgage.

Details:

Me:
Purchased alone in 2004
Interest only mortgage
Outstanding balance: £148K
Current value of house: £315K

Partner:
Lived here for 3.5 years
Does not currently contribute to mortgage
Does and will further contribute to improvements on property

What is fair in terms of a deed of trust?

Do I work on current value which can fluctuate? Do I try to do %'s?

How do I figure out what is fair but still protect my investment?

Unless you want to make an absolute gift to them, you do I think need to come up with a form of wording that gives them an interest in the property proportionate to the uplift in the value of the property caused by their contribution to improvements. They can also get an increased interest to the value of the mortgage they help pay off.

Any more than that and you're making them an immediate gift.

Is he going to pay towards the new mortgage or are you going to carry on paying it yourself?

I would base it on the current value as it stands when you put the property into trust.

How do you want to share the money?

If you are going to pay equally towards matters, what about you get the first £167k (the current amount of your equity provided you are not remortgaging for more) and then anything over that you split equally?

You could go for percentages, but that will become difficult if you re-mortgage in the future for more (you may not get back all you put in) as the mortgage gets deducted first before the proceeds are split.