If you plan to rest on the sea, and all three weeks (and maybe more) of the legitimate wish to leave it there, it makes sense to think about that instead of hotel rent a private apartment. Long-term rental apartments in Odessa will be much cheaper if the room rate per night in the hotels in Odessa on average multiplied by 25 days of stay in this wonderful, but this expensive city in the summer. What remember coming to town, in order to carry out his plan? 
First, accommodation in Odessa necessarily need to start looking within a couple of weeks before the trip, I use this for any of the popular among the inhabitants of the village newspaper with free ads. Thus, you will be able to phone in advance and agree on a suitable option. 
Also keep in mind that rent in Odessa, as in any other big city, shall take place without intermediaries, so if you do not want to rent for a month is not doubled (directly behind the apartment last month rent and service realtor) ,then you should learn to read messages between the lines. This task is simple. If a landlord rents an apartment: whether it is rent for a long time or you are considering an apartment in Odessa, the ad will never be too long. For an extra letter in the ad, this is an additional fee to the person who submits the proposal, but ordinary people, as a rule, it is unprofitable. So, looking very short, simple in form advertisement. If it is written that the price is negotiable - even better, so it really is not a real estate agency, with which to bargain not get. 
Although the commission of such transactions with homeowners has its disadvantages. It happens so that people that rent their homes, not quite adequate, especially those who donate an apartment in Odessa for picky guests, because many visitors but free housing is not enough. If you are dealing with an agent, he would justify his fee and will provide service at the highest level, to the point that will meet you at the train station and drive a car to a temporary location. Secondly, cooperation with the agency gives tenants a guarantee that housing really is reserved for him. While the owner may at any time change your mind and break his word, and you will not even be one to turn to the claims.