Enquiry about starting crypto exchange/brokerage platform

Hey guys,

I was looking into starting a crypto exchange/brokerage platform but I am not sure how complicated it is to start one and where to make one. I wanted one like satos.eu where you buy crypto (not too many, just like 5 types) at a fixed price. Without a wallet service, just a platform for purchase and selling.

Does anyone have more information about this? Would be greatly appreciated!

Thanks in advance.