The cost of maintaing a bike like that for a year would be next to nothing. Keep it clean and check you tyres regulalry and you'd be looking at no more than the price of a few innertubes (if you are unlucky with punctures), probably new tyres at the end of the year and some sort of lubrication to put on the chain and moving parts. Play your cards right and it'll be easily less than ?50. My advice would be to invest in a bike maintainence book or even a course, which isn't very expensive, and keep your bike cleanish and you'll never look back. I wince everytime I go into a bike shop and hear people being charged ?20+ for a change of innertube, it's the easiest job in the world!