A few people have asked me this now by PM also.
Basically, I trade prop from a UK firm based in London. I trade automated and semi automated systems. I prefer to stay a little anonamous so rather not say which firm but they are a big player on Eurex and, to lesser degree, CME and LIFFE. They also offer stocks and just about any other instument to people who know how to trade.
Anyway, my only point is that not all shops require money down if the individual (trader) is of high quality. The industry is full of both crooks and genuine firms offering real services. You just need to do some research and seperate the good from the bad.
To the OP - if you have no real trading experience (vs paper) with your system, you might have trouble convincing most props / arcades. There are hundreds of successful back tests out there being pitched around by crooks and idiots. That is why many might ask for money down as insurance. If you like, send me some details (product, system stats and trading frequency - not the actual strategy) and I'll take a look. If the system were really good, you could potentially even setup a structure to trade the strategy via a 3rd party and not even have to leave work.