[[XST]O_x]

Have a variable to store the time in which the lease will expire

Код:

House[houseid][ExpirationDate] = gettime() + 60 * 60 * 24 * 30 //The current timestamp with addition of 30 days, converted to seconds

And set a timer that will check every minute or every hour if the timestamp has been reached or exceeded

Код:

House[houseid][ExpirationTimer] = SetTimerEx("CheckTimestamp", 60 * 1000 * 60, true, "i", houseid);

forward CheckTimestamp(houseid);
public CheckTimestamp(houseid)
{
    if(gettime() >= House[houseid][ExpirationDate]) {
        //Date reached
        KillTimer(House[houseid][ExpirationTimer]);
        //Do whatever you want here
    }
    return 1;
}

That code would check every hour(to prevent spamming the server with checks) if the 30 days has passed.