Hot tub guys aren't plumbers, but they are specially trained hot tub engineers. That thing will need a huge amount of cleaning done to all the pipes for the jets, they will be full of algae and god knows what. It will need it's filter replacing and new silver balls, plus cleaning and refilling. ( a time consuming job). It also looks as though it doesn't have a lid on it which will need replacing. Just had to do this on mine, it was a 6 month wait for a new lid ( they have to come from the US) and cost £400. I would say given the state of that thing it should be between £500-£1000 to get it up and running again, and then if you don't check the water and balance the ph, chlorine etc daily it will soon be rank again. If that guy is going to do that in return for free advertising he is a mug. How many of her 'fan's' are likely to be potential customers for him? You are right about them needing to be earthed properly ( we had a special plug outlet installed for ours, again more cost) it can be fatal. We had friends whose 18 year old son was sadly electricuted by their hot tub ( not in the UK though, somewhere with dodgy wiring).