Bikes are generally pretty maintainable I would say. Some characteristics that I like about bikes that keep from me having to maintain them to much are:

• Internal gear hub: the gears are internal which means they don't get dirty as easily, don't wear the chain as quickly, and the chain doesn't need to be oiled as frequently either. Lastly, there's no real maintenance required of it, while still lasting a long time. Downsides are it's extra weight, and cost (if you're using it for urban biking, i would say the weight added is negligible)
• Check out whether rim breaks or disc brakes, or pedal breaks(forgot the name, but it's when you back pedal to brake) last longer and whether they require more maintenance. I know disc brakes are better performing and don't really wear out the bike rim in the same way rim brakes do, but I'm uncertain about their longevity. Disc brakes I believe. Are the more expensive option I believe.
• Dynamo hub for lighting (if you need it) is pretty expensive but also means not having to worry about your lights and their batteries wearing out, or having to reattach and detach them from your bike.
• Bike frame: I'm not too familiar with materials and their longevity, but I think if you avoid carbon fiber bikes (which are usually higher end) your frame will be very resilient.

Another important question is what will you be using it for? Urban biking? Mountain biking?