Without a great deal of luck or holding the car for a long time, I think it is very tough for an individual to make real money on a collector car. I currently have 3 vintage cars and have sold 3 over the years. I consider myself quite lucky to break even, and that usually requires some fuzzy math on my part to convince my wife I didn't lose any money and to rationalize the whole thing for myself. Only once did I make real money on a car. I only owned it for a few months so mostly luck. Actually the nice profit helped me to buy my GT !
It's pretty hard to time the market on collectible cars, unless you plan on holding them for a long time. Sure, guys who bought Gullwings in the 1970's for $7000 are doing great, but guys who bought muscle cars 5 years ago are eating their shorts. I typically tell friends the best car to buy is one that was over restored for too much money 5 years ago and now on a distress sale. If you have to restore or do a lot of work to a classic, it gets very expensive fast. On top of that, if you factor in the additional things you mentioned - insurance, storage, transport, commission to sell, maintenance etc..., don't buy one to make money. If one buys a car to show at major shows, restoration costs climb exponentially for the pursuit of perfection. Chroming, paint, body work, finding rare parts is a very expensive hobby.
The other comment I'll make is maintaining classics takes a lot of time ! Searching out parts and folks who can work on them (unless you do the work yourself) can be very time consuming. Living in steamy Florida, I enjoy climbing in my air conditioned GT, pushing the magic button and going.
These days I tend to think of classic cars as works of art where my primary enjoyment is looking at them and showing them, and my secondary enjoyment is driving them (after all, they don't typically have A/C and are quite slow). I don't think of them as an investment. If I make money, or don't lose much, I call it a victory.