As stated before, research the construction of the tub thoroughly before you purchase it. We bought a CalSpa a year ago and it is wonderful! It’s got a little waterfall jet, fiber optic lighting (that changes colors), and a “volcano jet”- basically a really huge jet that comes up from the middle of the floor with some huge pressure!
Look at the insulation and cabinet construction- I would recommend a foam insulated cabinet, as it helps keep the heat in (look for utility bills about $35-50 extra for the pump and heater- the extra insulation is worth it!). The main drawback of the foam insulation is that, if there were a leak in the jets/ supply lines, it may be hard to get to.
Consult an electrician to find out if your electrical service is large enough to handle the amps that a hot tub may draw ( ours required a 50 amp GFCI breaker- which means we had to upgrade our electrical service from 100 amps to 200 amps- to the tune of $1100). Certain code requirements must also be met (depending on your locale). We had to have a shutoff box located at least 6’ away from the edge of the tub, but within a direct line of site of the tub. Cable had to be 6/3, no more than 200’, etc…
Slab/ ground preparation is key, your hot tub weight will be in the tons- my CalSpa weighs 5915 pounds with 475 gallons of water in it! I poured my own 10’x10’ slab and saved a bunch of money. I used 2x6s for the forms, dug 10" deep, put 4" of crushed limestone down, compacted it, and poured a 5 1/2" slab with remesh in the center. Concrete cost was $178, wood $40.00. Obviously the key to the slab is making sure it is level and will stay that way.
Buy a good cover and a cover lift- the bestinvention for hot tubs. You can remove the cover with one hand, and it stores on the side of the hot tub… We had a tub at our old house without a lift, and it was a pain in the ***. Lift example
Try to get a tub with an ozonator- it helps to keep the tub clean and cuts down on the amount of chemicals needed. This is a big help, because it is not easy to keep the pH levels consistant if you are not used to it- took us about 2 months to get it right.
Just a few suggestions while I had time. If you have any other questions, just let me know- I’ll write more advice/ experiences later.