Hi Andrea, I found this old
thread and am not sure if you got an
answer.
Common hawthorne, Crataegus monogyna, starts to flower for me after only 4 years or so. I'm not sure if that is typical, usually I find that
trees take longer to reach maturity for me, so you may find that yours will fruit sooner, or could take longer.
As regards transplanting: generally if the tree is happy and is in a spot where it will be fine as a full size tree, then leave it be. It doesn't necessarily benefit from transplanting. If it is going to be unhappy or in the way after a few years - like under a power line, or too close to the house - then move it sooner rather than later (ie. whilst it is still quite small). I believe it is better to transplant deciduous trees in the dormant season. I would do it in early spring, but in some areas moving in autumn is supposed to be better, since the tree will carry on growing
roots over winter and that will get it off to a better start in spring.
I hope this helps.