Mark, this thread has been very useful to me as I am also recently smitten with the Hobie TI. I have wanted to try sailing for much of my adult life but the recent drought conditions here in central Texas have dashed any hopes of owning a trailer-able sailboat like a Catalina 22, and I can't imagine paying hundreds of dollars a month for a boat slip in a marina. Our boat ramps on Lake Travis are currently 50 ft. below useable level.
Then a few weeks ago I learned about the TI and have been on a similar quest to learn about it.
I just wanted to add a few items to your list of expenses albeit small ones from my compiled list of other stuff I need.
PFD's for 2 plus potential friends
First Aid Kit , onboard and more extensive onshore
Tool Kit - multitool etc.
spare paddle - maybe not needed on TI since it comes with two
mirage drive leashes
Gaffer tape ( much better than ductape )
made in Texas of course
waterproof cell phone containers
anchor and trolley kit
Popup canopy for shore to take a break from the sun
Currently planning to attend Demo Days at out local Hobie dealer.