How on Earth would someone be able to answer that comparison?
Of course a 911 is going to cost more than an Accord to maintain, regardless of the year.
Suffice it to say that if you can afford a 911 you can afford the maintenance. But really, you don't want to buy a 1999 911. It's cheaper than others for a reason. It's less desirable, and that's the first year of the 996 generation (funky headlights, water cooled vs classic air cooled).