In addition to buying and maintaining a vintage bike, depending on what it is you might also be challenged in just riding it, even if it's in top mechanical condition. For example you might need to be able to work a rocker clutch....with your foot! While shifting gears with your hand. If your vintage bike has a normal clutch and footshift, the gear selector might be on the right hand side.
And that vintage Indian you are admiring likely has the throttle on the left hand grip, and when you rotate the right hand grip that controls the spark advance. Twist your right wrist at the wrong time and you can foul out your plugs and you're coasting to a stop at the side of the road.
You might also have to learn to adjust your own engine oiler. Many old bikes had a total loss system, where you hand pumped oil into the engine at a steady rate, then stopped to drain it out every 500 miles or so.
The list goes on and on, and you certainly ARE capable of owning and operating a nice vintage bike, but you'll likely want to start learning to ride and wrench on something a little more modern.