Just to be absolutely clear before explaining, I am in no way a fan of this and I would much rather be provided hotac and all related expenses but it's not an option.
You get an extra 10 en an hour for about 1000 hrs on the run up to the command and once enrolled in the upgrade system.
Then when you start the training you have roughly 2 weeks where you are not earning whilst completing the ground school and sim.
Then you're line training where you will receive an extra 20 eu an hour due to being out of base and then once checked and completing your first 100 hrs from left seat in your training base you obviously are being paid captain money.
It all evens itself out really as you're flying a lot during that time so the 2 weeks off isn't too much of a hit.
As I say, far from ideal but the days where I've flown an 8 hour block and received an extra 160 eu for that day I have not spent anywhere near that amount in hotels and food - there are various tax benefits (all above board before the usual crew send my IP address to the revenue inspectors) as you're out of your base so you generally keep most of the extra money.