I agree with the previous 2 posts, the 3500, one ton vehicle is your best choice.
The only way a 2500, or 3/4 ton vehicle would factor in is over mileage. Seeing that carpet cleaning is a localized industry, even in a 300 mile radius, you’re not going to put on the mileage that would make a 3/4 a better option.
Also, your vehicle will always remain loaded, a job more suited for a 3500, plus factor in additional towing capacity, something that may not be a concern at the moment, but in the future, the added potential may prove handy.