Hookah systems are safe, I've been using them for years. They have an upright "snorkel" for air intake that is mounted a few feet and opposite side of the motor from the exhaust for the fresh air. Low pressure systems require a special low pressure regulator that is really cheap to buy comparitively. They have reserve air tanks in line that give you maybe a minutes air after the motor shuts down, plenty of time to get back up from thirty feet. Considering that they run for several hours on a tank of gas, this is generally not a problem.
They also make high pressure systems as well, for diving to depths greater than thirty feet. Or for two or more divers.
The TR-80 unit (low pressure) can supply enough air for two divers, if they're not working hard and starving each other for air. I've done it with mine, but I have also heard from others that theirs wouldn't, so its pretty tight as far as enough air for two divers.
If money is tight, I would look for a used unit and get a rebuild kit, which should cost (if you get lucky) less than the cost for getting SCUBA certified and buying your own regulator. They are simple units and easily rebuildable.