Nice setup i want to build a similar one and i have few questions.

How much time do you need to have the return on investment ?

Is it worth mining in Europe with the high electricity price ?

Does it make a lot of noise / heat ?

How did you found some cheap RX 570 ?

Thanks. 

>How much time do you need to have the return on investment ?
well, that depend of what do you mine, if you are mining ethereum only, it will take a long time to get ROI (maybe it's already too late for ethereum specifically. maybe)
If you just want to make fast $$$ then switch every day to the most profitable coin, but remember that mining is a hobby not a get rich scheme, with that mindset, mining has just started. :)

>Is it worth mining in Europe with the high electricity price ?
No idea if it's 'worth' but it's still profitable (at least in France, EDF standard charge are 0.14€/kWh, i pump continuously around 730 watt and with my current hashrate on ETH i make arround 7$ profit/day.
Depend really of which coin you are mining.

>Does it make a lot of noise / heat ?
Yeah, gpus fan make a lot of noise constantly, don't put a rig in your bedroom.
And yes too for the heat, i don't find that disturbing but definitely you will feel that the room is warmer compared to the rest, i guess you can have hard time during summer.

>How did you found some cheap RX 570 ?
I don't really have an advice for that, just lurk on ebay and on shops.
If you buy gpu from ebay, be careful, especially if it's from another miner.
Usually miners take care of their gpu for preserving lifespan, but you'll never know if someone abused the temperature, voltage etc...