As an property investor in the U.S. I would question the following before buying from anyone…

a) Can they provide you with a CURRENT INDEPENDENT valuation on their properties (called a BPO)

b) If they are selling you the properties at current market value why are they charging fees on top (you mention a $3K handling fee). If it is brokerage fees (can be up to 6%) the seller would normally pay this not the buyer. If it is just purely a sourcing fee are they also making a margin in the price they are selling to you at? If so why are they "double dipping"?
There are companies buying direct from the foreclosure auctions that will just add a fee on and you buy the property on an "as is" basis (obviously prices are way below current market value however you have to do all the work yourself to rehab, find tenants, insure etc.).

c) Have you done your homework on the area you are buying in? I would be very careful buying property in markets like Las Vegas, Florida, Phoenix etc. (just my opinion having invested there previously). These markets have come off the 2007 peak prices by 50-60% so may look great value but if you look at the S&P Home value indexes the past few months you will see these markets are still falling.

Usinvest could be a very good company to work with (sorry I don't know them) but just do your homework with no matter whom you buy from. Hope that helps!