[Alex_Valde]

Here you go mate, just delete that "COMMAND:" and uncomment that "dcmd_contract", I've done this quickly so...

pawn Код:

/*dcmd_contract*/COMMAND:(playerid, params[])
{
    new targetID,reason[128], money;
    if(!sscanf(params, "us[128]i", targetID, reason, money))
    {
        if(IsPlayerConnected(targetID))
        {
            new name[MAX_PLAYER_NAME], targetname[MAX_PLAYER_NAME], string[128];
            GetPlayerName(playerid, name, sizeof(name));
            GetPlayerName(targetID, targetname, sizeof(targetname));
            SetPlayerWantedLevel(targetID, 6);
            format(string, sizeof(string), " %s has place an contract on you. Reason: %s.",name, reason);
            SendClientMessage(targetID, 0xFFFFFFFF, string);
            format(string, sizeof(string), " You have placed a contract on %s for $%d",targetname, money);
            SendClientMessage(playerid, 0xFFFFFFFF, string);
            GivePlayerMoney(playerid, -money);
        }
        else return SendClientMessage(playerid,COLOR_RED, "Error: Player is not connected.");
    }
    else return SendClientMessage(playerid, COLOR_RED, "Usage: /contract [ID] [Reason] [Reward]");
    return 1;
}

I haven't tested it but it should work perfectly.
One more thing - You will need to make something like if some one kills that guy, he will get that reward, in this command I've made you won't get that.