I have no personal experience but there are frequent reports of some such agencies being scammy bastards, which isn't to say those are. The small print frequently allows them to make charges that aren't obvious from the off, untill you don't receive the revenue that you had expected.
Generally I think it falls into the category of "If it sounds too good to be true, it probably is". Given your distance, I'd look for a reputable managing agent and pay their fees. Finding one will require more than a single recommendation.