Welcome to the forum,it looks like you have a real challenge on your hands.
What is involved in the €500 challenge?
Obviously the budget is 500,but does that include any work needing done after buying the bike?
Is there a route to complete and is it for a charity?
you buy a bike older than 20 years have a budget of 150 euro . the difference between 500 euro and the money you bought it for will be defided by 2 and added to the budget .
you are not allowed to have owned the bike for more than a year prior to entering the challenge
brakes and tires are not subject to the budget (safety first)
in june the group is going to ride through europe ( about 4000 km )
here points will be given for multiple disiplines. the person who got the most points wins