Most systems show the evaporator coil after the blower, however, some air handlers show a configuration where it is before the blower. I don't have enough room above my vertical furnace to put an A coil. Would a horizontal coil between the filter and blower work?

Coils are always better on the discharge side of the unit. It prevents moisture from damaging the heat exchanger.

Do you have a mobile home? Many of these require the evaporator coil to be installed below the heat exchanger and blower almost floor level. Sometimes it's not the best way but the only way.

I have an old 2 story colonial with a yankee basement. If I put an A coil on top of the furnace I would have to cut the joists above it. From what I've seen heat exchangers rust anyway so I'm not too concerned with that. But, could that same condensate freeze the blower?

I have seen coils installed on the return side but it creates more concerns. You need to make sure you have a good air filter before the coil and a properly designed condensate trap. Pulling the cold air over the heat exchanger is not efficient and can reduce the life of the heat exchanger. Be sure to get a coil designed for the air flow direction you'll need. I'm not recommending this application but I have seen it done.