Buying during construction usually costs less and lets you choose the floor and position. In return, you get a promise instead of a key. What that promise is worth depends entirely on the contract.
Deadlines, written as a date
"The end of next year" is not a deadline. The contract must contain the handover date and state what happens if that date is not met. Without this second part, the deadline is just a wish.
Specifications, not descriptions
"Quality materials" means nothing. The contract must list what is included: the type of windows, the insulation, the heating system, the floors, the condition in which the apartment is handed over. If something is not on the list, don't assume it is included.
The payment schedule
Payments are usually tied to construction phases. Make sure the contract links them to completed, verifiable work, not simply to the passing of months. This is the mechanism that protects you if work stalls.
What happens with registration
The unit you are buying often does not yet exist as a separate unit in the register. The contract must state clearly who takes on the steps to register the building and form the units, and within what deadline after handover.
Ask specifically: when will I be able to go to the notary and then to the MCO? The answer should be a planned step, not an assumption.
Changes during construction
Buyers often ask for changes — one wall less, one socket more, a different type of tile. Agree on each in writing, with the price and the effect on the deadline. Verbal agreements on site get forgotten or are remembered differently by each side.
Who you are trusting
Look at what the investor has built before and whether those buildings were handed over. A company with completed, occupied buildings gives you a kind of security that no contract can replace.