When I was trying to get my first REO listing I treated BPOs like prospecting - except when you complete a BPO you normally will receivee a small stipend ($40-$60) on each one. I was happy to do this work for the BPO companies because I knew I needed to provide something of value to them before they would consider asking me to list a foreclosed property.
It may work out for some agents but in general I would be cautious about signing up with companies that require a monthly fee. Most agents that consistently list REO properties do so without subscribing to a any kind of an REO network. In almost every case, they started by completing BPOs. Myself included. I'm skeptical of all subscription services that claim to assign REO listings to agents. Several of these exists and none of them offer any guarantee that an agent in their "network" will receive an REO listing.
In order to become an reo vendor you either need to make an application with them directly if they sell their own properties or with the asset management compnay they use to sell their properties. By signing up does not always mean you are accepted. you are just on teh list if they have an opening, once they have an opening you need to build your expereince through completing bpos and such for them. Most companies reward their great agents with reo listings. Some will grade you or use a points system.
There are no short cuts or secrets other than hardwork.
i have a detailed blog you should check out with some more info on becoming an reo broker.