It all has to do with care over its first 103,000 miles.
90k service is fairly expensive but you are right you should be able to all of it yourself. I have the list at home; will try to remember to post it.

timing belt is due at 60k, 120k, 180k etc. (if it was not done before now and documented, I'd probably walk away.

new A/C unit...do you mean new evaporator? If so, was it flushed, cleaned etc--new dryer?

Water pump usually lasts for 120k+

check for replacement/repair of EVAP system and leaking Rear Main Seal

Also listen for air pump---about time for that to go if not already replaced.

Best of luck.