Since this is the first year for a lottery at Broad Street, there's no history to go on. There's a field limit of 40,000 but I haven't seen any info on how many of those are charity runners with guaranteed entry. Considering that the three main charities are the American Cnacer society, Students Run Philly Style, and Back on My Feet, I expect the number will be in the thousands. I also expect there will be slots reserved for runners connected with Blue Cross. Last year registration closed after five hours indicating a lot of demand. I'd suggest you consider entry through SRPS or Back on My Feet since the amount you need to raise is relatively modest ($500) compared to other charities.