Permission to Enter an Apartment Before Final Payment

Are there contracts where the buyer is allowed to move into the apartment even before the final payment?

In most contracts, the sale takes place with the final payment at the time of handing over possession, and therefore the contract states that the seller commits to selling and the buyer commits to buying, as the sale has not yet occurred with the first payment, and it is only a commitment to sell. This is why the money in the seller's hands is considered a loan. However, there are contracts that state that the seller sells and the buyer buys, and then the sale takes place with the first payment, and it is considered that the buyer is obligated since he has already purchased the property but has not yet paid for it in full, and in this case, the buyer is prohibited from doing favors for the seller.