Tenants in common percentage shares and additional borrowing help

stanners8

Hey everyone, 
So I'm needing some help working out percentage shares for my house. I bought the house a few years ago and it has been solely in my name, now we are adding my partner to the mortgage as tenants in common and we are having a declaration of trust drawn up. 

I have £67k equity in the house 
Valued at £170k 
But we are having additional borrowing of £41,100. To do the kitchen/garden up 

I'm just really confused how to protect my initial investment if things go wrong and we split. 

Any advice would be so welcome right now 🤣

Cheers 

getmore4less

Are they bringing any cash to the table.

How do you plan to split the mortgage

You could own 50:50 if you lend the oh 1/2 your 67k equity (and they lend you 1/2 their cash input)

If you want equity based then your 67k owns 39.4% the mortgage own the rest 60.6

If you pay 50:50 then you own 69.7% oh owns 30.3%.

Any future maintenance and improvements should be done at those %.