How much would a 1940s vintage ladies Schwinn bike go for?

MR is correct. Womens bikes are usually purchased so collectors can cannibalize them to restore mens bikes.

Unfortunately, there are VERY few parts that can be swapped on most bikes from that era. If the bike is in near pefect shape including original tires, it may be worth up to $100 or so... but I doubt that it would fetch much more.

Depends on condition, and how much some one want to pay for it.

you can go two ebay.com and put that in the search page

I can't give you an exact value but can say this ladies frames are worth much less then men's. Since you don't mention what model and what condition the bike is in I really can't even estimate. It's likely not very valueable.