unless your in wave 8, an organised trip there is easily possible, it just recruiers you to talk to some ppl and get them to help u with getting the cash(and at wave eight, there is always some spare money).
i don't really get what u mean with avail, but i think u mean to say that the only way of getting it is when the wave just starts? I'm trying to fix that. snipe had a thought about delaying it, and i got some idea's of my own too.
about that keeping the last zombie alive... sure you can do that, or you can go just before the wave ends(when there is only ten left) but the point is: if you realy want to use it in a efficient way, u will have to work together. meaning you can't camp there alone and there won't be an overflow of money