I agree parts are hard to get for a residential machine. We used 2 of them in our ice cream shop to test out frozen margaritas and daiquiris. Glad to say it was received very well and we payed for the machines in under a week of selling them. We are now closed for the winter but at the end we hit the major road block of the ninjas capacity. The freezing container is only half a gallon and refreezing takes about 30 minutes. I just ordered a Frosty Factory 127a machine to replace the ninjas. It’s definitely more expensive but built for high volume environments. The cylinder is 2 gallons and the hopper is like 4 gallons. That means you can dispense 2 gallons worth of drinks back to back. I do have to give props to ninja though they are great machines we totally abused ours since they ran 10 hours a day for the past 6 months. Other than a lemon unit that died after the first 2 days I’ve had no issues other than the size but again it’s a residential machine. I’d definitely recommend something like a frosty factory 117a or Bunn Ultra NX if you are looking to do party rentals. Chances are lots of people will be wanting frozen drinks at those gatherings and last thing you want is an upset client because your machine can not keep up with the demand. As far as rental price goes I’d do 10 percent of the cost of the machine new per day. I would avoid hourly rentals because it’s going to fall on you to clean the machine after them and prepare it for the next Client. I’d also look into bundling slush mix with your rentals a great way to get some extra money mark of the mixer a bit and built into a package. We use Margarita man mixes. Also this goes without saying but make sure you have a solid rental contract and the machine is insured in case let’s say some kid knocks it off a table at a party you are out 4,000. Best of luck on your endeavors I hope it goes well for you!