Hot tubs go great on decks; just make sure to evaluate the structural integrity of the deck accounting for the water and people that will be in the tub.
Another affordable technique. A small square wood platform will keep your hot tub safely off the ground...we prefer synthetic recycled decking material for its durability, yet pressure-treated decking is acceptable.
Crushed stone bases are popular in Maine and are the most affordable site preparation technique. We recommend at 6-8 inches of 3/4 inch jagged edge crushed stone, depending on the tub, and a pressure-treated wooden retention structure and an underground french drain (also of crushed stone) to insure no water pooling in the crushed stone [...]
While soil type can make a difference, we usually recommend a minimum of 4-6 inches of concrete, reinforced by wire mesh "rebar". We have a list of well-reviewed contractors for this type of work. Just email us and ask.