During the construction, it is very possible that the constructor is constructing a project on a field of the third person.
This is the way how the construction business mostly works in practice. Most of the contracts between landowners and the constructors are made like that: after starting the construction the floor easement is started.
Then, the landowners transfer the ownership of the detached sections(flats) to the constructor, in return of it the constructor encumber the section with hypnotic right in order to give a guarantee of proceeding the construction.
Depending on the contract, the owners release the Hyphoteks (mortgage) on the flats or other independent sections belonging to the constructor, when the constructor reaches the construction levels.
Another situation we are facing in practice is that the constructors are using credits from the banks and they encumber hypnotic in favor of Banks. We strongly suggest you stay away from these projects.
As above mentioned cases, there can be hypnotic on the deeds. That can be checked only in the deed. If there are no hypnotic or any other restrictions, it is also important to check the financial situation of the construction company in order to be sure that the constructor will proceed with the construction.
If there is a hypnotic on the deed in favor of the landowners, it is really good to know, if the construction company is a trustable big company and in a very good financial situation. (It depends on the investors.