Partner Wants Out of a Property: Fair Business Practice Exit?

[Rabih El-Khoury]

$126,000 property purchased by three partners, each putting the same amount of $42,000. Each partner holds the same number of shares, therefore. 

All cash inflows and outflows have been split 3-way. 

One of the partner now wants out (wants to sell their shares), the two others don't want to sell the property. 

Property has appreciated to ~$148,000 since purchase. 
Property turns a net profit every year. 

What's fair business practice for determining the value of these shares, i.e. the partner's exit package? 

Thanks!

R.