Mike,
The model # would be entirely up to what you feel your sales would be, the only bad thing is not having large enough to fufill the demand. I have the floor model 351, which is the sister to counter model 350. The only time I have trouble keeping up with demand is school shows (150 +) as they are hitting all at one time. Even then it only tales a few minutes to recover in the Taylor as the freezing is done around the product.
I have found a cure for this and make up a good amount of the 20 oz, mostly Blue Raspberry ahead of time. I use styrofoam cups to stop sweating and with the insulation value, and as cold as the drink is, it stays very servable when the bus hits the door.
I sell for same price as soft drinks, but that is because the base and flavors are made next door to one of my suppliers--no shipping costs
, so an ounce costs me less than soda. But people would pay a higher price for a slushie than soda.
I sell as much in winter as summer