Buy a carbon frame? Titanium? Aluminum?
Well, actually aluminum can corrode, too... "white rust". Carbon doesn't like impacts... and some say it explodes in strong sunlight. So that just leaves titanium.
Seriously, if it's rusting that badly on the outside after just one year, I'd be worried about the inside of the tubing, too. It probably looks worse than it is at this point... But it will continue to get worse and eventually weaken the steel.
I'd be tempted to strip the bike down, touch up the exterior (sand, prime, paint), then spray some rust preventative inside all the tubing. There are automotive products that would work... the names escape me at the moment.. restoration suppliers like Eastwood Company sell kits, but you wouldn't need all that much for a bike frame. It's
not thick, rubberized "undercoating" like you see in a lot of local auto parts stores.
One rust preventative is a mist that's sprayed inside car frames, settles into a thin, waxy surface coating covering all the internal surfaces. Heck, even a thorough spray of motor oil in there would help t some degree. Unfortunately, it means stripping the bike all the way down to the frame, and even then there will likely be some inaccessible areas. However, most of the tubing on a bike should have some sort of access to the inside, even if it's only a "weep hole" to allow condensation to drain out.
The ultimate "fix" for the outside surfaces would be to strip the bike down to bare metal (soda or sand blasting is the fastest way, but costs to have done) and then have it powder coated. Depending upon how much of the work you do yourself, that might cost $100 to $200. Just be sure that any powder coating is "UV Safe". Some of it isn't, and will degrade rapidly on anything used regularly outdoors. Powder coating is generally more durable and seals against moisture better than paint. But today there are some highly durable paints available, too, which would be another possibility.
But, any repainting or powder coating still wouldn't help with the inside surfaces of the tubing. So some sort of rust preventative would still be needed.