Its quite complex as a mini community/network. You might be able to get away with using BuddyPress as a cheaper version but it will still be several thousands of dollars to design and build
Charlie is on the money, a good estimate is around $5-$10k for a “cheap” solution but ultimately it depends on exactly what features you want / need and how much you want to spend.
Before getting quotes you need to write down a detailed brief on it so you know what you want, and know what you’re getting from the developer
And you will DEFINITELY want some form of RELEVANT evidence from them if previous work i.e. like this project or at least complex as its not an easy build
Yes indeed it will cost you several thousands of dollars to finish the project. Better to find out someone from Europe and possibly you could save a good amount of dollars. Check them out whether they have developed that kind of site ever before or not.