I have a site I used to sell my own portfolio of sites and domains. Now there are other people registered who are selling their own sites on mine, and I am getting commission for this. Something similar to sedo, only that I am not involved in the transfer. I just allow them to list and sell their sites. Is there any more space for this kind of business? Should I keep the site/domain and promote it or it is better to just sell it?
Well, if it's doing well, why not keep it? You should try and advertise it more and maybe you will be up there with the big sites like sedo. The bigger your userbase is, the more people will come: it's like a chain reaction. If you intend to sell it, then you should try and get more people using the site and earning more revenue before you sell it. This way you'll be able to sell it before
that's a real good start, i say development, promote and who knows, if your site become successful enough, the big companies might offer to buy it or struck a partnership
If i'm in your shoes i will keep promoting the site and make it a huge. And then consider selling it at good price