A saturated market?
One could make a go of it, but it's going to take deep pockets to out market the big players ... or something that makes your service much more attractive to the buyers or sellers.
I remember Bido.com - Bid on Bido - v1.1371 crashing on a hot auction.
I used to run this script on one of my domains, but I failed to market the site properly and I ended up using the domain for something else, now I'm not even using it. Go figure...
I am set up something like that. Only locally on my tongue, on line without charge. Too much fraud is on the internet, so just for this reason could fail. We will see, time will show whether the decision is positive.
Who does not try to, will never know ...