You will need
  • - monitoring similar offerings on the real estate market in their region;
  • - consultation of real estate professionals.
If the apartment is sold with a General consent of the owners as a whole, the option to divide between them the proceeds less expenses related to the preparation and registration of the transaction, in proportion to each and distribution in the same way the amounts referred to Trat seems to be the most fair.
If the share is sold, especially not isolated in nature, many of the factors that increase the cost of separate housing, completely lose value. For the buyer, which the area needs to stay more preferred options are presented in a communal room or in the hostel. The share usually only required for registration at the place of residence or stay, and for buyers of such a plan has a value of only one indicator - price.
It is clear that no buyer will not refuse, if he will give a share in the property for free, and even better - they pay for themselves. But such a plan is possible only in dreams. Even in this segment has its own demand and its offer, so that the laws of the market are in full force.
To present about what to expect, is to study similar and comparable deals in the print media and the Internet. This will allow to understand the rough framework, how much for housing this plan the sellers and how many buyers are willing to pay. It should be understood that the person giving the announcement of the sale, expects to receive for their property as much as possible, and the buyer is to give less for it. But that's not guaranteed either, so that price expectations are subject to correction.
More light on the situation shed advice in estate Agency (and better in several). It is not binding, and for this service the Agency, as a rule, do not take money. Besides, until you resolve the issue with the holders of the right of pre-emption (owners of other shares which you are required to make an offer to sell and a month to wait for the answer - and so with each decrease in price), to find you a buyer, no one will. But with respect to the amount on which you rely, rather, to enlighten you.