Without knowing how much you ride and what you ride its hard to say. With my experience, any machine will develop problems if you let it sit. Seals, gaskets, rubber parts, hoses and anything else meant to expand and contract with heat and cold will lose elasticity and ability to seal and you end up with problems.
If you plan to ride a lot, its definitely healthier for the bike but maintenance will come around a lot more quickly. You will find that changing your oil and air filter is easy and inexpensive and you can do it at home.
I found tires to be my biggest expense because I run sticky race compound rubber as I enjoy a more spirited ride. Spirited riding + sticky tires = new tires every 3k miles or so. Hard tires can last 7k miles.
Be prepared to do a valve adjustment anywhere between 10 - 15k miles depending on how aggressive you are on the gas.
If you keep your chain & sprocket lubed religiously, you can get a LOT more life out of them than expected.
So my answer is depending on these items above your expense to maintain your bike can vary greatly.