In my experience, the biggest things will be the age of the tires, if they are original or even replace early on, they are likely way out of date and will need to be changed. The next thing is the carbs. Unless it has been stored very well, they will likely have to be gone through. Jets may well be gummed up, floats may be sticking, etc. Then as you said, the fluids will need to be changed. Coolant hoses and etc. may or may not be bad. If it has been sitting a long time and even if it hasn't been, the rear shock may be leaking oil. A lot of them had the seals go bad even when not sitting. There is a member here who can rebuild it cheap or maybe even tell you how to do it. They are great bikes and if it's in good shape, will be worth the effort if the price is right.